Articles: Storage

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Disk Response Time and Average Positioning Speed

For 10 minutes IOMeter is sending a stream of requests to read and write 512-byte data blocks with a request queue of 1. The total of requests processed by each SSD is much larger than its cache, so we get a sustained response time that doesn’t depend on the SSD’s buffer size.

Intel SSDs have always had an extremely low response time at both reading and writing, and the X25-V series is no exception. The rest of the SSDs are somewhat slower but without such fatal shortcomings as we could see with the earlier SSDs based on the JM602B controller. The highest response time at writing is actually no higher than 0.5 milliseconds.

Take note that the 256MB drive from Western Digital has a higher response time at writing than its smaller-capacity cousin although the latter should theoretically have the same or somewhat worse response. Comparing the controllers, the JM618 in Toshiba’s version is somewhat worse at reading but much better at writing than the JM612 in WD’s version. But again, none of the SSDs betrays any serious problems in this test.

Random Read & Write Patterns

Now we will see how the performance of the drives in random read and write modes depends on the size of the requested data block.

We’ve got some interesting things at random reading. First, the pair of Intel X25-V drives in RAID0 are very good, competing and occasionally outperforming their SLC-based opponent. Second, the Intel controller loses its advantage on 32KB data blocks but is superior on smaller ones. Third, the JM612 controller in the WD drives is better than the JM618 in the Kingston V series.

Funnily enough, the graph of the 128GB model from WD is nowhere to be seen in the diagram although it is indeed there. At this scale, the results of the two SSDs from Western Digital are so similar that their graphs coincide.

We’ve got a lot of interesting things at writing. First, the RAID0 array with two X25-V is ahead of the X25-E on small data blocks. The single X25-V is good as well, although the flat stretch of its graph at 10,000 operations per second makes us suspect some architectural limitations.

Comparing the two models from Western Digital, the larger-capacity one delivers more stable results although falls behind its 128GB cousin on some data blocks. The JM618-based Kingston is faster than both drives from WD but cannot match the performance of the “value” X25-V.

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