Momentary disconnections with OCZ/Silicon Power? At such an attractively low price, the OCZ SSD has been selling well but some users have been complaining about a latency problem on this SSD when performing multiple tasks. As you will see below, the IOMeter tests underline a random access problem with the model. We have tried to see if there is a link.
We used IOMeter with 4KB operations and more or less random access on the OCZ Core V2 and the Samsung SLC SSD as well as on a VelociRaptor. First, here are the read results:
The SSD drives show a great superiority over classic hard drives here. When it comes to write results however, the figures are not so positive:
The performances drop to a lesser extent than for read speeds on the VelociRaptor, because of the cache, but it’s the SSD results that are significant here. The Samsung SSD doesn’t fall off anywhere near as much as the OCZ Core V2. After operations go over 25% random access, the drive can no longer respond more than 19 times a second to what the IOMeter throws at it and at 100% random access this drops to 4!
Worse, although the OCZ SSD response time varies between 0.26 and 224ms (1 divided by the number of I/Os), it has a maximum write response time of around 900ms
whatever the percentage of random access. In view of these scores, we can draw the conclusion that the higher the incidence of random access, the higher the frequency of this response time. This explains the saw-tooth pattern obtained in the sequential writing tests with applications such as HDTune and HDTach.
With the Samsung SSD, the maximum response time is 80ms and the average response varies between 0.14 and 8.8ms. The average for the VelociRaptor varies between 0.09ms and 4.59ms (long live the cache), with a maximum of 40ms.
The presence of a cache is supposed to cover the significant write latency but, in contrast to the Samsung and the Intel, the OCZ Core SSD has no SDRAM at all. As a result you have to rely on the JMicron controller buffers which hardly seem up to the job.
You will no doubt have understood that this is a significant limitation with lower end SSDs, especially with the OCZ Cores and the Silicon Power, which gives exactly the same results.