The problem is when the SLC cache runs out - as is possible for creative professionals transferring huge work files. Normal workloads rarely go beyond this huge cache, and that is enough to make the X8 lead the charts in almost all tests. The reason for the X8's stellar performance for normal workloads lies in this SLC cache. The X8, on the other hand, performs admirably with the SLC cache - For around 256GB of continuous writes, the drive provides 825 MBps+ of bandwidth before slipping down to around 150 MBps for the direct-to-QLC writes. Sequential Write to 90% of Disk Capacity - Performance Consistency (NVMe-Class) At 195 MBps, the drive already starts off with low expectations, and there is not much to write home about. On the other hand, the X6 starts off at around 200 MBps and goes down to around 35 MBps after 240GB of continuous writes. Sequential Write to 90% of Disk Capacity - Performance Consistency (SATA-Class)īoth the HP P600 and the ADATA SC680 show signs of a SLC cache. The internal temperature is recorded at either end of the workload, while the instantaneous write data rate and cumulative total write data amount are recorded at 1-second intervals. 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 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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