A fio workload is set up to write sequential data to the raw drive with a block size of 128K and iodepth of 32 to cover 90% of the drive capacity. Our Sequential Writes Performance Consistency Test configures the device as a raw physical disk (after deleting configured volumes). Use of SLC caching as well as firmware caps to prevent overheating may cause drop in write speeds when a flash-based DAS device is subject to sustained sequential writes. Fortunately, such workloads are uncommon for direct-attached storage devices, where workloads are largely sequential in nature. Many benchmarks use that scheme to pre-condition devices prior to the actual testing in order to get a worst-case representative number. Worst-Case Performance Consistencyįlash-based storage devices tend to slow down in unpredictable ways when subject to a large number of small-sized random writes. We analyze each of these in detail below. The latter is also important when used with battery powered devices such as notebooks and smartphones. Power users may also be interested in performance consistency under worst-case conditions, as well as drive power consumption. We also looked at the performance consistency for these cases. The performance of the storage bridges / drives in various real-world access traces as well as synthetic workloads was brought out in the preceding sections. Miscellaneous Aspects and Concluding Remarks
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