Towards fast profiling of storage devices regarding access sequentiality

Abstract

International audienceThis work presents a tool for storage device profiling named SeRRa. Our tool obtains the sequential to random throughput ratio for reads and writes of different sizes. Several optimizations aim at adapting applications’ access patterns in order to generate contiguous accesses for improved performance when accessing storage devices like hard disks. However, when considering other storage options like RAID arrays and SSDs, the access time ratio between contiguous and non-contiguous accesses may not compensate for these optimizations’ cost. In this scenario, the information provided by our tool could be used to dynamically decide if optimizations are beneficial for performance, an important task to provide I/O throughput. In order to provide this information efficiently, SeRRa employs benchmarks to obtain the values for a subset of the parameter space and estimates the remaining values through a linear model. Extensive test campaigns with our tool on nine storage devices have shown median errors of approximately 5% (up to 55%) while taking only 1/168 of the originally needed time

Parallel Storage Devices Profiling with SeRRa

“…We have executed tests using two measuring points per interval, as this configuration was the one with the best results in our previous analysis [Boito et al 2015]. We use up to four benchmark repetitions.…”

“…Multiple intervals, with different gaps, could be provided. The points at the extremes of the interval (in this example, 8 and 40KB) are always included on this step, since our previous analysis [Boito et al 2015] has shown that doing so improves approximations. 2.…”

“…However, obtaining this metric to a storage device can be a time-consuming task. In order to provide accurate results as fast as possible, SeRRa was developed in our previous work [Boito et al 2015]. This tool reports, for a storage device, the sequential to random throughput ratio for read and write operations with different request sizes.…”

Automatic I/O scheduling algorithm selection for parallel file systems

“…To represent platforms' characteristics, we use information provided by SeRRa , proposed in a previous work of ours . It provides the sequential to random throughput ratio for read and write operations with different request sizes.…”

“…On some SSDs, there is no difference between sequential and random accesses, but on others, this difference achieves orders of magnitude . The sequential to random throughput ratio on some SSDs surpasses what is observed on some HDDs . Therefore, approaches that aim at generating contiguous accesses (originally designed for HDDs) can greatly improve performance when used on SSDs that are also sensitive to access sequentiality.…”