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Solid State Drives (SSDs) have many attractive features, and they are well-positioned to replace traditional HDDs in cloud and enterprise storages. However, some specific features they have such as erase-before-write and limited erase count make this transition more challenging. To tackle the issues brought by these features, Flash Translation Layer (FTL) leverages functionalities such as Garbage Collection (GC) to provide free space by erasing the blocks and cleaning the stale data. This process occupies SSD resources and causes extra waiting time for normal IO requests, and ultimately increases response time. Cloud workloads include many applications with small random write access patterns which cause frequent GC invocations. Flash occupation at the time of GC causes inconsistent performance and increases tail latency which may in turn violate SLA in these applications. In this paper, we modify the conventional GC process and propose a Cache-assisted Garbage Collection (CachedGC). CachedGC postpones writing back valid pages during the GC, erases the block at the first possible time, and hence resumes normal SSD operations sooner. CachedGC reduces request response time and tail latency by reducing the effective latency of GC. Our experimental results using a variety of workloads show that CachedGC reduces read tail latency by 19% and improves write IOPS by as much as 27%.

Existing solid state drive (SSD) simulators unfortunately lack hardware and/or software architecture models. Consequently, they are far from capturing the critical features of contemporary SSD devices. More importantly, while the performance of modern systems that adopt SSDs can vary based on their numerous internal design parameters and storage-level configurations, a full system simulation with traditional SSD models often requires unreasonably long runtimes and excessive computational resources. In this work, we propose SimpleSSD, a highfidelity simulator that models all detailed characteristics of hardware and software, while simplifying the nondescript features of storage internals. In contrast to existing SSD simulators, SimpleSSD can easily be integrated into publicly-available full system simulators. In addition, it can accommodate a complete storage stack and evaluate the performance of SSDs along with diverse memory technologies and microarchitectures. Thus, it facilitates simulations that explore the full design space at different levels of system abstraction., Comment: This paper has been accepted at IEEE Computer Architecture Letters (CAL)

The system administrator, faces an arduous task of figuring out whether to consolidate storage workloads, which workloads to isolate, which workloads to co-locate, and how to reduce the interference on co-located workloads? This paper presents an approach to ease this arduous task. We consider different mixes of enterprise storage applications on a high-end SSD to study their performance, system throughput and fairness in their consolidated execution. The paper also considers a static approach using an integrated combination of resource partitioning and data placement to reduce the interference between the workloads.