Operating system level data tiering using online workload characterization

IEEE Trans. Emerg. Topics Comput.

2021

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I/O caching techniques are widely employed in enterprise storage systems in order to enhance performance of I/O intensive applications in large-scale data centers. Due to higher performance compared to Hard Disk Drives (HDDs) and lower price and nonvolatility compared to Dynamic Random-Access Memories (DRAM), Flash-based Solid-State Drives (SSDs) are used as a main media in the caching layer of storage systems. Although SSDs are known as non-volatile devices but recent studies have reported large number of data failures due to power outage in SSDs. To overcome the reliability implications of SSD-based I/O caching schemes, RAID-1 (mirrored) configuration is commonly used to avoid data loss due to uncommitted write operations. Such configuration, however, may still experience data loss in the cache layer due to correlated failures in SSDs. To our knowledge, none of previous studies have investigated the reliability of SSD-based I/O caching schemes in enterprise storage systems.In this paper, we present a comprehensive analysis investigating the reliability of SSD-based I/O caching architectures used in enterprise storage systems under power failure and high-operating temperature. We explore variety of SSDs from top vendors and investigate the cache reliability in mirrored configuration. To this end, we first develop a physical fault injection and failure detection platform and then investigate the impact of workload dependent parameters on the reliability of I/O cache in the presence of two common failure types in data centers, power outage and high temperature faults. We implement an I/O cache scheme using an open-source I/O cache module in Linux operating system. The experimental results obtained by conducting more than twenty thousand of physical fault injections on the implemented I/O cache with different write policies reveal that the failure rate of the I/O cache is significantly affected by workload dependent parameters. Our results show that unlike workload requests access pattern, the other workload dependent parameters such as request size, Working Set Size (WSS), and sequence of the accesses have considerable impact on the I/O cache failure rate. We observe a significant growth in the failure rate in the workloads by decreasing the size of the requests (by more than 14X). Furthermore, we observe that in addition to writes, the read accesses to the I/O cache are subjected to failure in presence of sudden power outage (the failure mainly occurs during promoting data to the cache). In addition, we observe that I/O cache experiences no data failure upon high temperature faults.

Section: Failure Characterization Of I/o Caches In Enterprise Storagementioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Evaluating Reliability of SSD-Based I/O Caches in Enterprise Storage Systems

Ahmadian

Taheri

IEEE Trans. Emerg. Topics Comput.

2021

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“…Filesystem metadata is one of the primary request types which is shown to be very efficient for caching [9], [10]. OODT [9] considers randomness and frequency of accesses to prioritize the data pages. To reduce the migrations between HDD and SSD, [11] considers the dirty state of the data pages in memory buffers.…”

Section: Previous Studiesmentioning

confidence: 99%

An Efficient Hybrid I/O Caching Architecture Using Heterogeneous SSDs

Salkhordeh

Hadizadeh

IEEE Trans. Parallel Distrib. Syst.

2019

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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 and neglected to address both parameters in suggested architectures. Moreover, the cost, reliability, and power consumption of such architectures is not evaluated. This paper proposes a hybrid I/O caching architecture that while offers higher performance than previous studies, it also improves power consumption with a similar budget. The proposed architecture uses DRAM, Read-Optimized SSD (RO-SSD), and Write-Optimized SSD (WO-SSD) in a three-level cache hierarchy and tries to efficiently redirect read requests to either DRAM or RO-SSD while sending writes to WO-SSD. To provide high reliability, dirty pages are written to at least two devices which removes any single point of failure. The power consumption is also managed by reducing the number of accesses issued to SSDs. The proposed architecture reconfigures itself between performance-and enduranceoptimized policies based on the workload characteristics to maintain an effective tradeoff between performance and endurance. We have implemented the proposed architecture on a server equipped with industrial SSDs and HDDs. The experimental results show that as compared to state-of-the-art studies, the proposed architecture improves performance and power consumption by an average of 8% and 28%, respectively, and reduces the cost by 5% while increasing the endurance cost by 4.7% and negligible reliability penalty.

“…Increasing number of I/O intensive applications such as Online Transaction Processing (OLTP), High Performance Computing (HPC), web, and email applications arises the demand in data-centers for high-performance storage systems. The most common approach to improving the performance of storage systems is to employ Solid-State Drives (SSDs) [1] in the caching layer of the disk subsystems [2], [3], [4], [5], [6], which are mainly built upon low-performance and lowreliable Hard Disk Drives (HDD) [7], [8], [9] or mid-range SSDs (as shown in Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

LBICA: A Load Balancer for I/O Cache Architectures

Ahmadian

Salkhordeh

2019 Design, Automation &Amp; Test in Europe Conference &Amp; Exhibition (DATE)

2019

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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 in significant performance degradation on burst accesses.In this paper, we propose a novel I/O cache load balancing scheme (LBICA) with adaptive write policy management to prevent the I/O cache from becoming performance bottleneck in burst accesses. Our proposal, unlike previous schemes, which disable the I/O cache or bypass the requests into the disk subsystem in burst accesses, selectively reduces the number of waiting accesses in the SSD queue and balances the load between the I/O cache and the disk subsystem while providing the maximum performance. The proposed scheme characterizes the workload based on the type of in-queue requests and assigns an effective cache write policy. We aim to bypass the accesses which 1) are served faster by the disk subsystem or 2) cannot be merged with other accesses in the I/O cache queue. Doing so, the selected requests are responded by the disk layer, preventing from overloading the I/O cache. Our evaluations on a physical system shows that LBICA reduces the load on the I/O cache by 48% and improves the performance of burst workloads by 30% compared to the latest state-of-the-art load balancing scheme.