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In Solid-State Drives (SSDs) with tens of ash chips and highly parallel architecture, we can speed up I/O operations by well-utilizing resources during page allocation. Propos- als already exist for using static page allocation which does not balance the IO load and its efficiency depends on access address patterns. To our best knowledge, there have been no research thus far to show what happens if one or more internal resources can be freely allocated regardless of the request address. This paper explores the possibility of using different degrees of dynamism in page allocation and iden- tifies key design opportunities that they present to improve SSD's characteristics  

The failure probability in SSDs increases when the number of Program/Erase (P/E) cycles increases. Traditionally, a group of SSDs are protected with parity disks, called SSD-based RAID. It has been shown that the reliability of RAIDs depends on the distribution of parities among SSDs. There are two main policies to distribute parities among SSDs in RAIDs, i.e., evenly and unevenly. By distributing parities evenly, all SSDs would wear out with the same rate, causing simultaneous failures of SSDs. By distributing parities unevenly, one of the SSDs in RAID may fail much earlier than the others. Both these two drawbacks, i.e., the simultaneous failures of SSDs and the rapid first failure of one... 

In recent years, Solid-State Drives (SSDs) have gained tremendous attention in computing and storage systems due to significant performance improvement over Hard Disk Drives (HDDs). The cost per capacity of SSDs, however, prevents them from entirely replacing HDDs in such systems. One approach to effectively take advantage of SSDs is to use them as a caching layer to store performance critical data blocks in order to reduce the number of accesses to HDD-based disk subsystem. Due to characteristics of Flash-based SSDs such as limited write endurance and long latency on write operations, employing caching algorithms at the Operating System (OS) level necessitates to take such characteristics... 

Data reduction technologies have proven their effectiveness to decrease the ever-growing demands on storage system capacities, but also introduce new complexity in the system I/O stack that can easily invalidate well-known best practices. In this paper, we conduct an extensive set of experiments on an enterprise all-flash storage (AFS) system equipped with an open-source data reduction module, i.e., RedHat VDO, and reveal novel observations on the performance gap between the state-of-the-art and the optimal AFS stack with integrated data reduction. We then offer cross-layer optimizations to enhance the performance of AFS, which range from deriving new optimal hardware RAID configurations up... 

Data reduction technologies have proven their effectiveness to decrease the ever-growing demands on storage system capacities, but also introduce new complexity in the system I/O stack that can easily invalidate well-known best practices. In this paper, we conduct an extensive set of experiments on an enterprise all-flash storage (AFS) system equipped with an open-source data reduction module, i.e., RedHat VDO, and reveal novel observations on the performance gap between the state-of-the-art and the optimal AFS stack with integrated data reduction. We then offer cross-layer optimizations to enhance the performance of AFS, which range from deriving new optimal hardware RAID configurations up... 

In Solid-State Drives (SSDs) with tens of ash chips and highly parallel architecture, we can speed up I/O operations by well-utilizing resources during page allocation. Propos- als already exist for using static page allocation which does not balance the IO load and its efficiency depends on access address patterns. To our best knowledge, there have been no research thus far to show what happens if one or more internal resources can be freely allocated regardless of the request address. This paper explores the possibility of using different degrees of dynamism in page allocation and iden- tifies key design opportunities that they present to improve SSD's characteristics  

The wear-out of flash-based Solid-State Drives (SSDs) is a main concern that significantly affects their reliability. One major parameter that accelerates SSD wear-out is the number of write-cycles committed to flash chips. The number of write-cycles in SSD-based disk subsystem is highly dependent on the erasure code implemented in Redundant Array of Independent Disks (RAIDs). In this paper, we investigate the impact of erasure codes and the configuration of storage subsystems (i.e., the number of disks participated in the RAID array and stripe unit size) on the endurance of storage systems. The number of write-cycles is considered as a metric to evaluate the endurance of storage system. We... 

Over the past decades, Redundant Array of Independent Disks (RAIDs) have been configured based on mechanical characteristics of Hard Disk Drives (HDDs). With the advent of Solid-State Drives (SSDs), configurations such as stripe unit size can be far from the characteristics of SSDs. In this paper, we investigate the effect of stripe unit size on the endurance and the overall I/O performance of an SSD-based RAID array and compare the optimal stripe unit size with the suggested stripe unit sizes for HDD-based RAID. To this end, we first examine the number of extra page reads and writes imposed by write requests, and then observe the corresponding impact on the overall throughput and the... 

Solid-State Drives (SSDs) are recently employed in enterprise servers and high-end storage systems in order to enhance performance of storage subsystem. Although employing high speed SSDs in the storage subsystems can significantly improve system performance, it comes with significant reliability threat for write operations upon power failures. In this paper, we present a comprehensive analysis investigating the impact of workload dependent parameters on the reliability of SSDs under power failure for variety of SSDs (from top manufacturers). To this end, we first develop a platform to perform two important features required for study: A) a realistic fault injection into the SSD in the... 

In recent years, enterprise Solid-State Drives (SSDs) are used in the caching layer of high-performance servers to close the growing performance gap between processing units and storage subsystem. SSD-based I/O caching is typically not effective in workloads with burst accesses in which the caching layer itself becomes the performance bottleneck because of the large number of accesses. Existing I/O cache architectures mainly focus on maximizing the cache hit ratio while they neglect the average queue time of accesses. Previous studies suggested bypassing the cache when burst accesses are identified. These schemes, however, are not applicable to a general cache configuration and also result... 

The wear-out of flash-based Solid-State Drives (SSDs) is a main concern that significantly affects their reliability. One major parameter that accelerates SSD wear-out is the number of write-cycles committed to flash chips. The number of write-cycles in SSD-based disk subsystem is highly dependent on the erasure code implemented in Redundant Array of Independent Disks (RAIDs). In this paper, we investigate the impact of erasure codes and the configuration of storage subsystems (i.e., the number of disks participated in the RAID array and stripe unit size) on the endurance of storage systems. The number of write-cycles is considered as a metric to evaluate the endurance of storage system. We... 

Erasure codes are widely used in data storage systems to protect against disk failures. Employing erasure codes in an array of Solid-State Drives (SSDs) in storage systems necessitates designers to revisit different characteristics in comparison to Hard Disk Drives (HDDs), due to non-mechanical property of SSDs. One of the most important characteristics of SSDs is their limitation on the number of Program/Erase (P/E) cycles. By taking into account the characteristics of SSDs, this paper presents a comprehensive analysis to investigate the effects of three well-known erasure codes on the endurance and performance of SSD-based disk subsystems. The three erasure codes, i.e., Reed-Solomon,... 

Erasure codes are applied in both HDD and SSD storage systems to improve the reliability. The design of erasure codes for SSD-based systems should be performed with respect to a specific feature of SSDs, i.e., endurance. Endurance is defined as the number of Program/Erase (P/E)-cycles that one SSD can endure for reliable operation. The common metric for comparing the endurance of two systems is the number of P/E-cycles, which is yielded by time-consuming simulations. This paper proposes two new metrics called DPD-factor and GDP-pattern, for comparing the effect of erasure codes on the endurance of systems based on their encoding designs, without simulation. With respect to the endurance,... 

Storage subsystem is considered as the performance bottleneck of computer systems in data-intensive applications. Solid-State Drives (SSDs) are emerging storage devices which unlike Hard Disk Drives (HDDs), do not have mechanical parts and therefore, have superior performance compared to HDDs. Due to the high cost of SSDs, entirely replacing HDDs with SSDs is not economically justified. Additionally, SSDs can endure a limited number of writes before failing. To mitigate the shortcomings of SSDs while taking advantage of their high performance, SSD caching is practiced in both academia and industry. Previously proposed caching architectures have only focused on either performance or endurance... 

Increasing usage of Solid-State Drives (SSDs) has greatly boosted the performance of storage backends. SSDs perform many internal processes such as out-of-place writes, wear-leveling, and garbage collection. These operations are complex and not well documented which make it difficult to create accurate SSD simulators. Our survey indicates that aside from complex configuration, available SSD simulators do not support both sync and discard requests. Past performance models also ignore the long term effect of I/O requests on SSD performance, which has been demonstrated to be significant. In this article, we utilize a methodology based on machine learning that extracts history-aware features at... 

All-flash storage (AFS) systems have become an essential infrastructure component to support enterprise applications, where sub-millisecond latency and very high throughput are required. Nevertheless, the price per capacity ofsolid-state drives (SSDs) is relatively high, which has encouraged system architects to adoptdata reduction techniques, mainlydeduplication andcompression, in enterprise storage solutions. To provide higher reliability and performance, SSDs are typically grouped usingredundant array of independent disk (RAID) configurations. Data reduction on top of RAID arrays, however, adds I/O overheads and also complicates the I/O patterns redirected to the underlying backend SSDs,... 

Solid State Drives (SSDs) have recently emerged as a high speed random access alternative to classical magnetic disks. To date, SSD designs have been largely based on multi-channel bus architecture that confronts serious scalability problems in high-end enterprise SSDs with dozens of flash memory chips and a gigabyte host interface. This forces the community to rapidly change the bus-based inter-flash standards to respond to ever increasing application demands. In this paper, we first give a deep look at how different flash parameters and SSD internal designs affect the actual performance and scalability of the conventional architecture. Our experiments show that SSD performance improvement... 

Over the past decade, storage has been the performance bottleneck in I/O-intensive programs such as online transaction processing applications. To alleviate this bottleneck with minimal cost penalty, cost-effective design of a high-performance disk subsystem is of decisive importance in enterprise applications. Data tiering is an efficient way to optimize cost, performance, and reliability in storage servers. With the promising advantages of solid-state drives (SSDs) over hard disk drives (HDDs) such as lower power consumption and higher performance, traditional data tiering techniques should be revisited to use SSDs in a more efficient way. Previously proposed tiering solutions have... 

In recent years, high interest in using Virtual Machines (VMs) in data centers and cloud computing has significantly increased the demand for high-performance data storage systems. A straightforward approach to providing a high-performance storage system is using Solid-State Drives (SSDs). Inclusion of SSDs in storage systems, however, imposes significantly higher cost compared to Hard Disk Drives (HDDs). Recent studies suggest using SSDs as a caching layer for HDD-based storage subsystems in virtualized platforms. Such studies neglect to address the endurance and cost of SSDs, which can significantly affect the efficiency of I/O caching. Moreover, previous studies only configure the cache... 

One of the main issues in Solid State Drive (SSD)-based storage systems is endurance which is directly affected by the number of Program/Erase (P/E) cycles. The increment of P/E cycles increases the bit error rate threatening the reliability of SSDs. Erasure codes are used to leverage the reliability of storage systems but they also affect the number of P/E cycles based on their code pattern. A lower dependency between data and parities in the code pattern may lead to smaller number of P/E cycles providing better endurance. This paper introduces an Endurance Aware EVENODD (EA-EO), which minimizes the dependency between data and parities in the coding pattern. A simulation environment is used...