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With cloud assistance, mobile apps can offload their resource-demanding computation tasks to the cloud. This leads to a scenario where computation tasks in the same program run concurrently on both the mobile device and the cloud. An important challenge is to ensure that the tasks are able to access and share the files on both the mobile and the cloud in a manner that is efficient, consistent, and transparent to locations. Existing distributed file systems and network file systems do not satisfy these requirements. Current systems for offloading tasks either do not support file access for offloaded tasks or do not offload tasks with file access. The paper addresses this issue by designing and implementing an application-level file system called Overlay File System (OFS). To improve efficiency, OFS maintains and buffers local copies of data sets on both the cloud and the mobile device. OFS ensures consistency and guarantees that all the reads get the latest data. It combines write-invalidate and write-update policies to effectively reduce the network traffic incurred by invalidating/updating stale data copies and to reduce the execution delay when the latest data cannot be accessed locally. To guarantee location transparency, OFS creates a unified view of the data that is location independent and is accessible as local storage. We overcome the challenges caused by the special features of mobile systems on an application-level file system, like the lack of root privilege and state loss when application is killed due to the shortage of resource and implement an easy to deploy prototype of OFS. The paper tests the OFS prototype on Android OS with a real mobile app and real mobile user traces. Extensive experiments show that OFS can effectively support consistent file accesses from computation tasks, no matter whether they are on a mobile device or offloaded to the cloud. In addition, OFS reduce both file access latency and network traffic incurred by file accesses.

Key-value stores are increasingly adopting LSM-trees as their enabling data structure in the backend block storage, and persisting their clustered data through a block manager, usually a file system. In general, a file system is expected to not only provide file/directory abstraction to organize data but also retain the key benefits of LSM-trees, namely, sequential and aggregated I/O patterns on the physical device. Unfortunately, our in-depth experimental analysis reveals that some of these benefits of LSM-trees can be completely negated by the underlying file level indexes from the perspectives of both data layout and I/O processing. As a result, the write performance of LSM-trees is kept at a level far below that promised by the sequential bandwidth offered by the storage devices. In this paper, we address this problem and propose LDS, an LSM-tree Direct Storage system that manages the storage space based on the LSM-tree objects and provides simplified consistency control by leveraging the copy-on-write nature of the LSM-tree structure, to fully reap the benefits of LSM-trees. Running LevelDB, a popular LSM-tree based key-value store, on LDS as a baseline, comparing that to LevelDB running on three representative file systems (ext4, f2fs, btrfs) with HDDs and SSDs, respectively, we evaluate and study the performance potentials of LSM-trees. Evaluation results show that the write throughputs of LevelDB can be improved by from 1.8× to 3× on HDDs, and from 1.3× to 2.5× on SSDs, by employing the LSM-tree friendly data layout of LDS.

NEC-2 output reports are quite voluminous and have long lines that make them difficult to read and difficult to print. A convenient way to view them is to open the file in WordPad using the command “Wordpad CALL.OUT”. To conveniently print a hard copy of the file, select the entire file and reduce the font to size 6 so the long lines will fit on 8½ × 11 paper in the portrait orientation. A larger font can be used to print it in the landscape orientation.

Due to their massive popularity, image files, especially JPEG, offer high potential as carriers of other information. Much of the work to date on this has focused on stenographic ways of hiding information using least significant bit techniques but we believe that the findings in this project have exposed other ways of doing this. We demonstrate that a digital certificate relating to an image file can be inserted inside that image file along with accompanying metadata containing references to the issuing company. Notwithstanding variations between devices and across operating systems and applications, a JPEG file holds its structure very well. Where changes do take place, this is generally in the metadata area and does not affect the encoded image data which is the heart of the file and the part that needs to be verifiable. References to the issuing company can be inserted into the metadata for the file. There is an advantage of having the digital certificate as an integral part of the file to which it applies and consequently travelling with the file. We ultimately prove that the metadata within a file offers the potential to include data that can be used to prove integrity, authenticity and provenance of the digital content within the file. Keywords: Secure authentication, Integrity, Digital certificates, Security, Network security

Due to users’ network flow requirement and usage amount nowadays, TCP/IP networks may face various problems. For one, users of video services may access simultaneously the same content, which leads to the host incurring extra costs. Second, although nearby nodes may have the file that a user wants to access, the user cannot directly verify the file itself. This issue will lead the user to connect to a remote host rather than the nearby nodes and causes the network traffic to greatly increase. Therefore, the named data network (NDN), which is based on data itself, was brought about to deal with the aforementioned problems. In NDN, all users can access a file from the nearby nodes, and they can directly verify the file themselves rather than the specific host who holds the file. However, NDN still has no complete standard and secure file transfer protocol to support the ciphertext transmission and the problem of the unknown potential receivers. The straightforward solution is that a sender uses the receiver's public key to encrypt a file before she/he sends the file to NDN nodes. However, it will limit the behavior of users and incur significant storage costs of NDN nodes. This paper presents a complete secure file transfer protocol, which combines the data re-encryption, satisfies the requirement of secure ciphertext transmission, solves the problem of the unknown potential receivers, and saves the significant storage costs of NDN nodes. The proposed protocol is the first one that achieves data confidentiality and solves the problem of the unknown potential receivers in NDN. Finally, we also provide formal security models and proofs for the proposed FTP-NDN.

It is quickly becoming more common that users interact not just with a single computing device, but rather with multiple, heterogeneous, computing devices such as desktop computers, laptops, smart phones, smart televisions, tablet PCs, and video game consoles. This capability requires a new computing platform, called the N-screen platform differing in several ways from the traditional computing platform. Under the N-screen platform, users are likely to switch their workplace from one device to another. The attendant requirement for such a capability is providing file synchronization among the multiple devices. However, the current systems have limitation to provide this functionality due to lack of standard protocol. In this paper, we explore the development of a new file transfer protocol to support file synchronization for the N-screen network. Based upon the considered requirements and defined protocol, we expect to efficiently support a practical, virtual file synchronization system.

A middleware is proposed to optimize file fetch process in transparent computing (TC) platform. A single TC server will receive file requests of large scale distributed operating systems, applications or user data from multiple clients. In consideration of limited size of servers memory and the dependency among files, this work proposes a middleware to provide a file fetch sequence satisfying: (1) each client, upon receiving any file, is able to directly load it without waiting for pre-required files (i.e. receive and load); and (2) the server is able to achieve optimization in reducing overall file fetch time cost. The paper firstly addresses the features of valid file fetch sequence generating problem in the middleware. The method solves the concurrency control problem when the file fetch is required for the multiple clients. Then it explores the methods to determine time cost for file fetch sequence. Based on the established model, we propose a heuristic and greedy (HG) algorithm. According to the simulation results, we conclude that HG algorithm is able to reduce overall file fetch time roughly by 50% in the best cases compared with the time cost of traditional approaches. A middleware solution is proposed to optimize file fetch process in transparent computing (TC) environment.The method solves the concurrency control problem when the file fetch is required for the multiple clients.We propose a heuristic and greedy (HG) algorithm.HG algorithm can reduce overall file fetch time roughly by 50% in the best cases compared with the time cost of traditional approaches.

File systems that employ write-optimized dictionaries (WODs) can perform random-writes, metadata updates, and recursive directory traversals orders of magnitude faster than conventional file systems. However, previous WOD-based file systems have not obtained all of these performance gains without sacrificing performance on other operations, such as file deletion, file or directory renaming, or sequential writes. Using three techniques, late-binding journaling , zoning , and range deletion , we show that there is no fundamental trade-off in write-optimization. These dramatic improvements can be retained while matching conventional file systems on all other operations. BetrFS 0.2 delivers order-of-magnitude better performance than conventional file systems on directory scans and small random writes and matches the performance of conventional file systems on rename, delete, and sequential I/O. For example, BetrFS 0.2 performs directory scans 2.2 × faster, and small random writes over two orders of magnitude faster, than the fastest conventional file system. But unlike BetrFS 0.1, it renames and deletes files commensurate with conventional file systems and performs large sequential I/O at nearly disk bandwidth. The performance benefits of these techniques extend to applications as well. BetrFS 0.2 continues to outperform conventional file systems on many applications, such as as rsync, git-diff, and tar, but improves git-clone performance by 35% over BetrFS 0.1, yielding performance comparable to other file systems.

With emerging “pay-as-you-go object storage” services, file system backup to object storage is an attractive option in terms of total cost of ownership. However, if a failure or a disaster occurs, a conventional backup system with object storage requires a long time to recover the necessary data since it must restore the entire directory structure of the file system from object storage before accessing the data. In this paper, a new backup method, which achieves on-demand restore as part of file system backup to object storage, is proposed. On-demand restore is a function that restores only a certain directory or file according to the request from an end user. The proposed method backs up relationships between a file and an object on a directory basis in order to efficiently handle the relationships in the restore. It is experimentally shown that the proposed method reduces the response time of file access involving restore by over an order of magnitude.

The convergence of high-performance computing and big data, which has become known as the field of extreme big data, is problematic in that file creation in storage systems such as distributed file systems is not optimized. That is, the large workload leads to the simultaneous creation of many files by many processes when creating checkpoints. The need to improve the file creation processes prompted us to design a scale-out distributed file system for post-petascale systems named PPFS. PPFS consists of PPMDS, a scale-out distributed metadata server, and PPOSS, a scalable distributed storage server for flash storage. High file creation performance of PPMDS was achieved by using a key-value store for metadata storage and non-blocking distributed transactions to update multiple entries simultaneously. PPOSS depends on PPOST, an object storage system that manages underlying low-level storage, such as Fusion IO ioDrive, a flash device connected through PCI express supporting OpenNVM. High file creation performance was attained by implementing the PPFS prototype using file creation optimization, termed bulk creation, to reduce the amount of communication between PPMDS and PPOSS. Moreover, to enhance the I/O performance of PPOSS when the client process and PPOSS run on the same node, PPOSS accesses the local storage device directly. The prototype implementation of PPFS with file creation optimization achieves 119,000 operations per second for file creation when using five metadata servers and 128 client processes, thereby exceeding the performance of IndexFS 2.17 times. With local access optimization, PPOSS reached its limit at a block size of 16 KiB, an improvement of 1.5 times compared to before optimization. Furthermore, this evaluation indicates that PPFS has scalability on file creation and IO performance, that is required for post-petascale systems.

The first step in using R is to download R from the Internet. R can be downloaded for the modern operating systems Windows, OS X, and Linux. In this chapter, you will learn how to download and install R and the 30 basic packages as well as how to install other packages and update R. You will also learn how to use R in individual folders within the file system of the computer.

The emerging technologies of persistent memory, such as PCM, MRAM, provide opportunities for preserving files in memory. Traditional file system structures may need to be re-studied. Even though there are several file systems proposed for memory, most of them have limited performance without fully utilizing the hardware at the processor side. This paper presents a framework based on a new concept, “File Virtual Address Space”. A file system, Sustainable In-Memory File System (SIMFS), is designed and implemented, which fully utilizes the memory mapping hardware at the file access path. First, SIMFS embeds the address space of an open file into the process’ address space. Then, file accesses are handled by the memory mapping hardware. Several optimization approaches are also presented for the proposed SIMFS. Extensive experiments are conducted. The experimental results show that the throughput of SIMFS achieves significant performance improvement over the state-of-the-art in-memory file systems.

Cloud providers offer several storage services for their users in efficient manner. Cloud users are allowed to store their data in cloud. The data leakage, lack of proper security control policy, and weakness in the data security are the main worries of the companies. We intended to propose a secure cloud storage system RSA-ABC algorithm for encryption and decryption process. Initially the user will login with the aid of private key and public key. Then send a request to the data base administrator for upload a file in a cloud. In this phase we will give one time password and keys. Then the DBA will verify that data and accept that file and encrypt that file and stored in to the cloud server. If the user want that file means they send a request to DBA continue the same process after they will decrypt the file and send to the user.

The emerging non-volatile memory technologies provide a new choice for storing persistent data in memory. Therefore, file system structure needs re-studying and re-designing. Our goal is to design a framework that gives high-performance in-memory file accesses and allows a file whose data can be stored across memory and block device. This paper presents a novel unified framework for in-memory and hybrid memory file systems based on the concept that each file has a contiguous "File Virtual Address Space". Within this framework, the file access for in-memory data can be efficiently handled by address translation hardware and the virtual address space of file. The file accesses for data in block devices are handled by a dedicated page fault handler for file system. A file system called Hybrid Memory File System (HMFS) is implemented based on this framework. Experimental results show that the throughput of HMFS approaches the memory bus bandwidth in best cases. Compared with in-memory file systems, HMFS reaches 5 times, 2.1 times, and 1.6 times faster than EXT4 on Ramdisk, RAMFS, and PMFS, respectively. Compared with EXT4 on SSD and EXT4 using page cache, HMFS also achieves 100 times and tens of times performance improvement, respectively.

As the number of file I/O intensive mobile applications increase, in-memory file systems have gained attention. In-memory file systems provide a fast access to file data, but the main memory of the corresponding mobile devices often suffers due to its capacity limit. To provide mobile applications with more free space, the swap mechanism has been an essential technique for the overcoming of this space insufficiency; however, the existing swap mechanism is inadequate for the file I/O of mobile applications. In this study, a new in-memory file system is devised to improve the current swap mechanism in the legacy in-memory file system, whereby strip-based layouts with separated file-swap partitions are used and unnecessary file- I/O overheads are eliminated. To evaluate the proposed in-memory file system, experiments with the file-I/O benchmark were conducted. The experiment results show that, compared to the current swap scheme, the proposed swap scheme improves the overall performance by ten times on average1.

Recent cloud infrastructures provide competitive performances and operation costs for many internet services through pay-per-use model. Particularly, object storages are highlighted, as they have unlimited file holding capacity and allow users to access the stored files anytime and anywhere. Several lines of research are based on cloud-backed file systems, which support traditional POSIX interface rather than RESTful APIs via HTTP. However, these existing file systems handle all files with uniform size backing objects. Consequently, the accesses to cloud object storages are likely to be inefficient. In our research, files are profiled according to characteristics, and appropriate backing unit sizes are determined. We experimentally verify that different backing unit sizes for the object storage improve the performance of cloud-backed file systems. In our comparative experiments with S3QL, our prototype cloud-backed file system shows faster performance by 18.6% on average.

File Time information has a significant meaning in digital forensic investigation. File time information in Linux Ext4 (Extended File System 4) environment is the Access Time, Modification Time, Inode Change Time, Deletion Time and Creation Time. File time is variously changed by user manipulations such as creation, copy and edit. And, the study of file time change is necessary for evidence analysis. This study analyzes the change in time information of files or folders resulting from user manipulations in Linux operating system and analyzes ways to determine real time of malware infection and whether the file was modulation.

When many processes issue write operations alternately on Log-structured File System (LFS), the created files can be fragmented on the file system layer although LFS sequentially allocates new blocks of each process. Unfortunately, this file fragmentation degrades read performance because it increases the number of block I/Os. Additionally, read-ahead operations which increase the number of data to request at a time exacerbates the performance degradation. In this paper, we suggest a new cleaning method on LFS that minimizes file fragmentation. During a cleaning process of LFS, our method sorts valid data blocks by inode numbers before copying the valid blocks to a new segment. This sorting re-locates fragmented blocks contiguously. Our cleaning method experimentally eliminates 60% of file fragmentation as compared to file fragmentation before cleaning. Consequently, our cleaning method improves sequential read throughput by 21% when read-ahead is applied.

As smart devices are revolutionized in recent years, people may generate enormous amount of various sized data and store them in the local or remote file system in their daily lives. With cheaper and easy to use private cloud storage appliances helping to handle the increasing demand of storing and sharing big volume of data, effective file deduplication schemes can greatly increase the space efficiency in private cloud storage systems as well as preserve network bandwidth. In the paper, we aim at designing and implementing several file deduplication schemes built in the private cloud storage appliance, based on different duplication checking rules, including file name, file size, and file partial/full content hash value. Experiment results show using partial content hashing based file deduplication scheme achieves a reasonably balanced performance without overutilized limited local computational resources.

In content based file sharing peer-to-peer (P2P) [1] network model nodes share files directly with each other without a centralized server. In such a file sharing system, nodes meet and exchange requests and files in the format of text, short videos, and voice clips in different interest categories. Content is various and large file sharing such as the multimedia content is required with the rapid development of the wireless communication technology. File sharing can also mean having an allocated amount of personal file storage in a common file system. A P2P content based file sharing system, for efficient file searching, threshold takes advantage of node mobility by designating stable nodes, which have the most frequent contact with community members, as community coordinators for intra community searching, and highly mobile nodes that visit other communities frequently as community ambassadors for intercommunity searching. The large file sharing needs more stable end to end path and long transmission time. Last but not least, more relationship between nodes will be used to promote the file sharing process. Content based file sharing is helpful for taking certain decisions during file transmission. These decisions will benefit in proper utilization of network resources. In this paper content-based file sharing scheme using threshold is proposed. The user's interest is determined by the proposed scheme before searching and sharing the files in the peer-to-peer network. The resources in the network are utilized as per the contents of the files to be shared. The performance evaluation show that proposed system significantly lowers transmission cost and improves file sharing success rate compared to current methods.

Nowadays, most of the information is stored digitally. Digital information is from a high level of view it is just an array of bits. In order to figure out its real meaning special software which interprets it is required. Therefore, if by evolution of technology this software cannot be executed anymore there is potential risk that also the data interpreted by it becomes not useful. The goal of Digital Preservation is to stop occurrences of such phenomenon. Data is commonly stored in files each file has a specific format or structure, by knowing it user can figure out the real meaning of raw data stored in the file as an array of bits. Digital Preservation considers valid file format as a perquisite for file to be in usable form, with valid is meant that a specific file is structured conform its declared file format. In this paper we throw a spotlight on the accuracy and capability of these file validation tests. Therefore, we present some open source software which are able to automatically identify and verify the file format. We focus more on file types they can identify, and how they work in large scale data sets.

Outsourcing a file to a remote cloud storage provides several benefits, including scalability, accessibility, data replication and considerable cost saving. Unfortunately, when we send a file to a remote cloud storage server, we do not know if this file is intact. To address this problem, we present a remote file possession checking protocol. In this protocol, we use three technologies: Firstly, we design a kind of file block tag whose security is based on the discrete logarithm problem (DLP); secondly, we use probability checking method to improve its effectiveness; thirdly, we use tag aggregation method to reduce its communication cost. Our theory analysis and experiment results show that our protocol is practical and secure.

The processing of massive numbers of small files is a challenge in the design of distributed file systems. Currently, the combined-block-storage approach is prevalent. However, the approach employs the traditional file systems such as ExtFS and may cause inefficiency when accessing small files randomly located in the disk. This paper focuses on optimizing the performance of data servers in accessing massive numbers of small files. We present a Flat Lightweight File System (iFlatLFS) to manage small files, which is based on a simple metadata scheme and a flat storage architecture. iFlatLFS is designed to substitute the traditional file system on data servers and can be deployed underneath distributed file systems that store massive numbers of small files. iFlatLFS can greatly simplify the original data access procedure. The new metadata proposed in this paper occupies only a fraction of the metadata size based on traditional file systems. We have implemented iFlatLFS in CentOS 5.5 and integrated it into an open source Distributed File System (DFS), called Taobao FileSystem (TFS), which is developed by a top B2C service provider, Alibaba, in China and is managing over 28.6 billion small photos. We have conducted extensive experiments to verify the performance of iFlatLFS. The results show that when the file size ranges from 1 to 64 KB, iFlatLFS is faster than Ext4 by 48 and 54 percent on average for random read and write in the DFS environment, respectively. Moreover, after iFlatLFS is integrated into TFS, iFlatLFS-based TFS is faster than the existing Ext4-based TFS by 45 and 49 percent on average for random read access and hybrid access (the mix of read and write accesses), respectively.

Minnaard proposed a novel method that constructs a creation time bound of files recovered without time information. The method exploits a relationship between the creation order of files and their locations on a storage device managed with the Linux FAT32 file system. This creation order reconstruction method is valid only in non-wraparound situations, where the file creation time in a former position is earlier than that in a latter position. In this article, we show that if the Linux FAT32 file allocator traverses the storage space more than once, the creation time of a recovered file is possibly earlier than that of a former file and possibly later than that of a latter file on the Linux FAT32 file system. Also it is analytically verified that there are at most n candidates for the creation time bound of each recovered file where n is the number of traversals by the file allocator. Our analysis is evaluated by examining file allocation patterns of two commercial in-car dashboard cameras.

The B ε -tree File System , or B e trFS (pronounced “better eff ess”), is the first in-kernel file system to use a write-optimized data structure (WODS). WODS are promising building blocks for storage systems because they support both microwrites and large scans efficiently. Previous WODS-based file systems have shown promise but have been hampered in several ways, which B e trFS mitigates or eliminates altogether. For example, previous WODS-based file systems were implemented in user space using FUSE, which superimposes many reads on a write-intensive workload, reducing the effectiveness of the WODS. This article also contributes several techniques for exploiting write-optimization within existing kernel infrastructure. B e trFS dramatically improves performance of certain types of large scans, such as recursive directory traversals, as well as performance of arbitrary microdata operations, such as file creates, metadata updates, and small writes to files. B e trFS can make small, random updates within a large file 2 orders of magnitude faster than other local file systems. B e trFS is an ongoing prototype effort and requires additional data-structure tuning to match current general-purpose file systems on some operations, including deletes, directory renames, and large sequential writes. Nonetheless, many applications realize significant performance improvements on B e trFS. For instance, an in-place rsync of the Linux kernel source sees roughly 1.6--22 × speedup over commodity file systems.

Mosts user of internet and smart phone has certificate, and uses it when money transfer, stock trading, on-line shopping, etc. Mosts user stores certificate in a hard disk drive of PC, or the external storage medium. In particular, the certification agencies are encouraged for user to store certificate in external storage media such as USB memory rather than a hard disk drive. User think that the external storage medium is safe, but when it is connect to a PC, certificate may be copied easily, and can be exposed to hackers through malware or pharming site. Moreover, if a hacker knows the user`s password, he can use user`s certificate without restrictions. In this paper, we suggest secure management scheme of the private key file using a password of the encrypted private key file, and a USB Memory`s hardware information. The private key file is protected safely even if the encrypted private key file is copied or exposed by a hacker. Also, if the password of the private key file is exposed, USB Memory`s container ID, additional authentication factor keeps the private key file safe. Therefore, suggested scheme can improve the security of the external storage media for certificate.

This paper proposes a new approach, called file concealer (FC), to conceal files in a computer system. FC modifies metadata about a file in NTFS (New Technology File System) to hide the file. Unlike traditional hooking methods which can be easily detected by antivirus software, experimental results show that it is difficult for antivirus software to detect the files hidden by FC. Moreover, to enhance the concealment capability of FC, FC also rearranges the order of some data sectors of a hidden file. As a result, even if another person finds the original sectors used by the hidden file, it is difficult for him to recover the original content of the hidden file. Experimental results show that even data recovery tools cannot restore the content of a hidden file. All information that is required to restore a hidden file is stored in a file, called recovery file hereafter. When a user uses FC to hide a file, the user can specify any file as a host file, such as an image file, to which the recovery file will be appended. As a result, the user can easily restore a hidden file; however, it is difficult for other person to detect or restore the hidden file and the related recovery file.

At present, as the amount of digitized information is increasing geometrically, the importance of digitized information as critical clues from the perspective of criminal investigation is also increasing. The importance of digital forensics has also magnified accordingly. As a fundamental technique of digital forensics, recovery of data deleted to conceal information is extremely important and needs to be studied. Although file system types and versions are diversified, sufficient studies have not been performed. The XFS file system was designed to process huge files, and thus it is expected to be applied in server systems. In this paper, we analyze the XFS file system using its structure and metadata information; then, we propose a technique to recover the deleted files through previous analysis results, and verify it through testing.

Efficient file query is important to the overall performance of peer-to-peer (P2P) file sharing systems. Clustering peers by their common interests can significantly enhance the efficiency of file query. Clustering peers by their physical proximity can also improve file query performance. However, few current works are able to cluster peers based on both peer interest and physical proximity. Although structured P2Ps provide higher file query efficiency than unstructured P2Ps, it is difficult to realize it due to their strictly defined topologies. In this work, we introduce a Proximity-Aware and Interest-clustered P2P file sharing System (PAIS) based on a structured P2P, which forms physically-close nodes into a cluster and further groups physically-close and common-interest nodes into a sub-cluster based on a hierarchical topology. PAIS uses an intelligent file replication algorithm to further enhance file query efficiency. It creates replicas of files that are frequently requested by a group of physically close nodes in their location. Moreover, PAIS enhances the intra-sub-cluster file searching through several approaches. First, it further classifies the interest of a sub-cluster to a number of sub-interests, and clusters common-sub-interest nodes into a group for file sharing. Second, PAIS builds an overlay for each group that connects lower capacity nodes to higher capacity nodes for distributed file querying while avoiding node overload. Third, to reduce file searching delay, PAIS uses proactive file information collection so that a file requester can know if its requested file is in its nearby nodes. Fourth, to reduce the overhead of the file information collection, PAIS uses bloom filter based file information collection and corresponding distributed file searching. Fifth, to improve the file sharing efficiency, PAIS ranks the bloom filter results in order. Sixth, considering that a recently visited file tends to be visited again, the bloom filter based approach is enhanced by only checking the newly added bloom filter information to reduce file searching delay. Trace-driven experimental results from the real-world PlanetLab testbed demonstrate that PAIS dramatically reduces overhead and enhances the efficiency of file sharing with and without churn. Further, the experimental results show the high effectiveness of the intra-sub-cluster file searching approaches in improving file searching efficiency.

Journaling file systems are widely used in modern computer systems as they provide high reliability at reasonable cost. However, existing journaling file systems are not efficient for emerging PCM (phase-change memory) storage because they are optimized for hard disks. Specifically, the large amount of data that they write during journaling degrades the performance of PCM storage seriously as it has a long write latency. In this paper, we present a new journaling file system for PCM, called Shortcut-JFS, that reduces write traffic to PCM by more than half of existing journaling file systems running on block I/O interfaces. To do this, we devise two novel schemes that can be used under byte-addressable I/O interfaces: 1) differential logging that journals only the modified part of a block and 2) in-place checkpointing that eliminates the overhead of block copying. We implement Shortcut-JFS on Linux 2.6.32 and measure the performance of Shortcut-JFS compared to those of existing journaling and log-structured file systems. The results show that the performance improvement of Shortcut-JFS against Ext4 and LFS is 54 and 96 percent, respectively, on average.

Large-scale small file storage for original pages degrades performance of search engines. In this paper, we first analyze the disadvantages of the existing EXT3 file system in accessing small files. Then, the rate and speed of compression algorithms are verified to choose a proper storage compression algorithm. Meanwhile, we design an original page oriented file organization structure and a read---write query tree to store the large-scale small files which need no modification. The accessing response time and disk space waste are remarkably decreased when search engines use these techniques to store original-page small files.

Linux environment that is commonly used at embedded systems supports various file systems as Ext2, FAT, NTFS, etc. The file system that is equiped on the embedded system is mostly implemented on mini hard disk or flash memory. The types of the file system of the system make an effect on the performance of a application programs. The factors of file system performance on a same media are block read, block write and block free time. On these factors, block read and block free time are not so different according to the type of file systems. This paper evaluates the performance benchmark of file systems supported by linux about block allocation and write performance. The results obtained from various experiments shows the characteristics of each file system.

In this paper, we propose a PC's self-monitoring system for protecting illegal outflow of important personal files, which are managed in the Windows environment PC. This paper is based on the idea that it should be a read (access) file operation in order to outflow files through the network. To compare the information (name, some content) obtained from all operations of the reading of the 'Windows File System Driver' and captured transmission packets of mini port of 'Windows NDIS (Network Driver Interface Specification) Driver', and, if two pieces of information match, this system will determine the transmission to user. In this paper, tentatively, we developed a function to gather file information about file read operation and developed a function for transmission packet capture. This demonstration implementation showed that the proposed process has validity and the proposed process verified that it does not significantly affect the PC's performance.

DFSCQ is the first file system that (1) provides a precise specification for fsync and fdatasync, which allow applications to achieve high performance and crash safety, and (2) provides a machine-checked proof that its implementation meets this specification. DFSCQ's specification captures the behavior of sophisticated optimizations, including log-bypass writes, and DFSCQ's proof rules out some of the common bugs in file-system implementations despite the complex optimizations. The key challenge in building DFSCQ is to write a specification for the file system and its internal implementation without exposing internal file-system details. DFSCQ introduces a metadata-prefix specification that captures the properties of fsync and fdatasync, which roughly follows the behavior of Linux ext4. This specification uses a notion of tree sequences---logical sequences of file-system tree states---for succinct description of the possible states after a crash and to describe how data writes can be reordered with respect to metadata updates. This helps application developers prove the crash safety of their own applications, avoiding application-level bugs such as forgetting to invoke fsync on both the file and the containing directory. An evaluation shows that DFSCQ achieves 103 MB/s on large file writes to an SSD and durably creates small files at a rate of 1,618 files per second. This is slower than Linux ext4 (which achieves 295 MB/s for large file writes and 4,977 files/s for small file creation) but much faster than two recent verified file systems, Yggdrasil and FSCQ. Evaluation results from application-level benchmarks, including TPC-C on SQLite, mirror these microbenchmarks.

It is challenging to simultaneously achieve multicore scalability and high disk throughput in a file system. For example, even for commutative operations like creating different files in the same directory, current file systems introduce cache-line conflicts when updating an in-memory copy of the on-disk directory block, which limits scalability. ScaleFS is a novel file system design that decouples the in-memory file system from the on-disk file system using per-core operation logs. This design facilitates the use of highly concurrent data structures for the in-memory representation, which allows commutative operations to proceed without cache conflicts and hence scale perfectly. ScaleFS logs operations in a per-core log so that it can delay propagating updates to the disk representation (and the cache-line conflicts involved in doing so) until an fsync. The fsync call merges the per-core logs and applies the operations to disk. ScaleFS uses several techniques to perform the merge correctly while achieving good performance: timestamped linearization points to order updates without introducing cache-line conflicts, absorption of logged operations, and dependency tracking across operations. Experiments with a prototype of ScaleFS show that its implementation has no cache conflicts for 99% of test cases of commutative operations generated by Commuter, scales well on an 80-core machine, and provides on-disk performance that is comparable to that of Linux ext4.

In the big data era, the distributed file system is getting more and more significant due to the characteristics of\ud its scale-out capability, high availability, and high performance. Different distributed file systems may have different design goals. For example, some of them are designed to have good performance for small file operations, such as GlusterFS, while some of them are designed for large file operations, such as Hadoop distributed file system. With the divergence of big data applications, a distributed file system may provide good performance for some applications but fails for some other applications, that is, there has no universal distributed file system that can produce good performance for all applications. In this\ud paper, we propose a hybrid file system framework, HybridFS, which can deliver satisfactory performance for all applications. HybridFS is composed of multiple distributed file systems with the integration of advantages of these distributed file systems. In HybridFS, on top of multiple distributed file systems, we have designed a metadata management server to perform three functions: file placement, partial metadata store, and dynamic file migration. The file placement is performed based on a decision tree. The partial metadata store is performed for files whose size is less than a few hundred Bytes to increase throughput. The dynamic file migration is performed to balance the storage usage of distributed file systems without throttling performance. We have implemented HybridFS in java on eight nodes and choose Ceph, HDFS, and GlusterFS as designated distributed file systems. The experimental results show that, in the best case, HybridFS can have up to 30% performance improvement of read/write operations over a single distributed file system. In addition, if the difference of storage usage among multiple distributed file systems is less than 40%, the performance of HybridFS is guaranteed, that is, no performance degradation.

Accidental misuse of shared files by authorised users is a predominant problem. This paper proposes a well-known static analysis approach, namely a type system, to prevent such accidental misuse. We develop a type system that intercepts commands issued by users in a file system and enforces policies on each file. Commands issued by users to manipulate files will be subject to type checking by the type system. Type-checked commands are then guaranteed to not violate policies of the files. The focus of this paper is on a particular policy that allows owners of files (users who created files) to specify the number of times a file can be read by limiting the number of times a file can be copied. Therefore, a file can be read as much as it can be copied. If the file cannot be copied, then it can be read only once. This approach can be extended to other properties.

Cloud storage services are pervasive nowadays. Many cloud storage services use distributed file systems as their backend storage systems. Some research results on file-size distribution of file systems show that file systems contain lots of small files. Therefore, this paper proposed a hybrid distributed file system based on Ceph and HDFS that can deliver satisfactory write throughputs for a cloud storage system with 80–90% small files and 10–20% large files. The experimental results show that the file allocation mechanism without RAM disk caching can improve the write throughputs of Ceph and HDFS by approximately 10% to 50%. While the one with RAM disk caching can have up to 200% write throughputs improvement.

We present Nswap2L-FS, a fast, adaptable, and heterogeneous storage system for backing file data in clusters. Nswap2L-FS particularly targets backing temporary files, such as those created by data-intensive applications for storing intermediate results. Our work addresses the problem of how to efficiently and effectively make use of heterogeneous storage devices that are increasingly common in clusters. Nswap2L-FS implements a two-layer device design. The top layer transpar- ently manages a set of bottom layer physical storage devices, which may include SSD, HDD, and its own implementation of network RAM. Nswap2L-FS appears to node operating systems as a single, fast backing storage device for file systems, hiding the complexity of heterogeneous storage management from OS subsystems. Internally, it implements adaptable and tunable policies that specify where data should be placed and whether data should be migrated from one underlying physical device to another based on resource usage and the characteristics of different devices. We present solutions to challenges that are specific to supporting backing filesystems, including how to efficiently support a wide range of I/O request sizes and balancing fast storage goals with expectations of persistence of stored file data. Nswap2L-FS defines relaxed persistence guarantees on individual file writes to achieve faster I/O accesses; less stringent persistence semantics allow it to make use of network RAM to store file data, resulting in faster file I/O to applications. Relaxed persistence guarantees are acceptable in many situations, particularly those involving short-lived data such as temporary files. Nswap2L-FS provides a persistence snapshot mechanism that can be used by applications or checkpointing systems to ensure that file data are persistent at certain points in their execution. Nswap2L-FS is implemented as a Linux block device driver that can be added as a file partition on individual cluster nodes. Experimental results show that file-intensive applications run faster when using Nswap2L-FS as backing store. Additionally, its adaptive data placement and migration policies, which make effective use of different underlying physical storage devices, result in performance exceeding that of any single device.

The advent of Persistent Memory (PM), which is anticipated to have byte-addressable access latency in par with DRAM and yet nonvolatile, has stepped up interest in using PM as storage. Hence, PM storage targeted file systems are being developed under the premise that legacy file systems are suboptimal on memory bus attached PM-based storage. However, many years of time and effort are ingrained in legacy file systems that are now time-tested and mature. Simply scrapping them altogether may be unwarranted. In this paper, we look into how we can leverage the maturity ingrained in legacy file systems to the fullest, while, at the same time, reaping the high performance offered by PM. To this end, we first go through a thorough analysis of legacy Ext4 file systems, and compare it with NOVA, PMFS, and Ext4 with DAX extension, which are new PM file systems available in Linux. Based on these analyses, we then propose the Persistent Memory Adaptation Layer (PMAL) module that is lightweight (roughly 180 LoC) and can easily be integrated into legacy file systems to take advantage of PM storage. Using Ext4, we show that the performance of PMAL integrated Ext4 is in par with PM file systems for the Filebench and key-value store benchmarks.

Proper identification is important for providing secure facilities and services to user. Cloud computing is involved in our day to day life as it offers several services, storage spaces, applications etc. As the usage increases, vulnerability and security threats arose need to be studied and rectified. As a part of this, proper authentication need to be done before allowing file uploading to cloud. Compared with traditional identification methods, authentication system using biometric are more reliable and universal. Since biometric cannot be lost or forgotten it provides more reliability and security. So biometric provide more security because it requires physical person to be authenticated. Stealing the biometric values by hacker attack will be protected by biometric cryptosystem. This enable users to upload a file safely from their computer and have it saved on the web server's file system. This would provide the basis for easy ways of storing and retrieving data directly within the database which involves a bit more code than working with data through the file system. Additionally, in order for a user to view or download data they must be presented with a URL to that data. If the data resides on the web server's file system, the URL would be a straightforward process. And if the data is stored in the database, a web page needs to be created and retrieve and return the data from the database. Further, if the data is stored on the file system, the demand and network congestion between the database server and web server will be less than when the data is stored directly within the database. Multi-biometric cryptosystem offer high authentication accuracy, wider population coverage and strong security compared to single biometric cryptosystem.

The aim of this paper is to design a system that has benefits equally for the client (cloud storage user) and the cloud storage provider. For the benefit of user, an improved security model for the data stored on the cloud is provided by encrypting the data even before uploading the file to the storage server. On the other side, the capacity of the cloud storage is optimally utilized by avoiding redundant storage of the same file on the server. Encrypting the same file by using two different algorithms produces two different encrypted files which in turn affects the performance by the de-duplication concept of the service provider. So an efficient mechanism which generates the hash value of the text and uses this hash value towards encrypting the data is proposed which uses hash values with unique file identifier. While the client uploads file to the cloud database, the unique id of the file is compared with those stored into the server. The proposed algorithm called Temporal Data De-duplication Algorithm (TDDdA) is used to get better performance of data storage in cloud. Since our approach is based on time, the read and write response time of the cloud data is linearly reduced. Increased security is achievable through our proposed model.

This chapter describes the details of SCION configuration files. All SCION configuration files are represented in JSON [42] format.

According to the intelligence of the malicious code to extract the executable file in physical memory is emerging as an import researh issue. In previous physical memory studies on ex ecutable file extraction which is targeting running files, they are not extracted as same as original file saved in disc. Therefore, we need a method that can extract files as same as original one saved in disc and also can analyze file-information loaded in physical memory.In this paper, we provide a method that executable file extract ion by analyzing information of Windows kernel file object. Also we analyze the characteristic of physical memory loaded fi le data from the experiment and we demonstrate superiority because the suggested method can effectively extract more of or iginal file data than the existing method.Keywords: Physical Memory Forensic, File Mapped Data, File Object I.서 론 최근 디지털 포렌식 연구에서는 하드디스크를 이 접수일(2014년 8월 6일), 수정일(2014년 9월 11일) 게재확정일(2014년 9월 12일)†주저자, k-dupe@nate.com‡교신저자, hhu@ensec.re.kr(Corresponding author)

Aiming at the file transmission problem between electronic controller for an engine and the portable test equipment based on AT91SAM9263 and Linux, the Interlnk/Intersvr software and their communicating protocol are analyzed and studied which used by electronic controller. The message format and communicating process are made clear by putting up protocol analysis environment at laboratory and source code analysis, FAT file system structure and its access methods are studied, and the file transmission function of test equipment has been fulfilled. The results of test indicate that the desired goals have been reached.

Digital devices are increasingly being used in various crimes, and therefore, it becomes important for law enforcement agencies to be able to investigate and analyze digital devices. Accordingly, there is an increasing demand for digital forensic technologies which can recover the data concealed or deleted by criminals that are of prime importance. There are various digital forensic tools available for Windows-based systems and relatively a few of those for Linux-based systems. Thus, this paper suggests a deleted file recovery technique for the Ext 2/3 filesystem, which is commonly used in Linux. The research involved the analysis of the Ext filesystem structure, file storage structure, and metadata information of file. The shortcomings of the existing methods and methods implemented by the proposed technique to address them are presented. Further, a comparison of the performance of the proposed technique and that of the existing methods is presented.

It is first extended the log4j and then applied the log file distribution function of log4j in E-Commerce service system in this paper. In this way, it can avoid all log information are centralized interspersed in a single log file, effectively disperse the log information of different concerns, easy to monitor and analyze E-Commerce service system operation status. Key words: Log4j, dynamic log file, extension, e-commerce services

With the increasing amount of personal data stored in public storage, users are losing control of their physical data, putting their data information at risk of theft or being compromised. Traditional secure storage systems either require users to completely trust the storage provider or impose the considerable burden of managing files on file owners; such systems are inapplicable in the practical cloud environment. This paper addresses these challenging problems by proposing a new secure system architecture and implementing a stackable secure storage system named Shield, in which a proxy server is introduced to be in charge of authentication and access control. We propose a new variant of the Merkle Hash Tree to support efficient integrity checking and file content update; further, we have designed a hierarchical key organization to achieve convenient keys management and efficient permission revocation. Shield supports concurrent write access by employing a virtual linked list; it also provides secure file sharing without any modification to the underlying file systems. A series of evaluations over various real benchmarks show that Shield causes about 7%~13% performance degradation when compared with eCryptfs but provides enhanced security for user's data.