In the Database pattern the SSD is processing a stream of requests to read and write 8KB random-address data blocks. The ratio of read to write requests is changing from 0% to 100% with a step of 10% throughout the test while the request queue depth varies from 1 to 256.
You can click this link to view the tabled results for IOMeter: Database pattern.
We will build diagrams for request queue depths of 1, 16 and 256.
The overall trends are clear enough, even though not so easy to distinguish in the tangle of graphs. The full-capacity IBIS products are in the lead, joined by the RevoDrive 240 GB which proves that its dual-controller design is a viable solution.
This test seems to depend not on the number of memory access channels but on the total amount of memory and, consequently, on the pool of spare blocks ready for writing. On the other hand, it wouldn’t be correct to claim that the number of memory channels is absolutely unimportant as is indicated by our JBOD sample which takes last place here.
As the request queue grows longer, the IBIS models become unchallenged. On the other side of the spectrum we see three losers: the 50GB and 80GB models which have two flash controllers and a reduced number of memory chips connected to each, and the RevoDrive which we switched into JBOD mode.
Winding up this part of our tests, we will build diagrams showing the performance of each SSD at five different request queue depths.
Comparing the performance of the different-capacity IBIS series products, we can see that the models with reduced number of flash memory chips have a performance hit at high percentages of writes. This is especially clear with the 100GB model in which each SF1200 controller has only four, not eight, channels to access flash memory. But when it comes to reading, these SSDs produce similar results.
The RevoDrive series isn’t as good as the OCZ IBIS although did well against conventional SSDs in our earlier tests. It is only the senior RevoDrive models with a full set of flash memory chips per controller that can compete with the IBIS series. The junior ones are slower, both at writing and reading. The RevoDrive x2 is somewhere in between. It might be able to compete with its quad-controller cousins if it were not for its reduced capacity.
It is the RevoDrive we switched into JBOD mode that proves to be the weakest link. It is slower than its cousins everywhere, proving the fact that modern SSDs benefit greatly from doubling the number of memory access channels by means of an internal RAID controller.