Performance in Intel IOMeter Sequential Read & Write Patterns

The array receives a stream of read/write requests with a request queue depth of 4. Every minute the size of the data block changes, so we can see the dependence of the linear read/write speed on the size of the data block. The results for the WriteBack mode are listed in the following table:

For better reading, we divide the arrays into two groups in the diagrams:

The advantages of the RAID arrays that consist of many HDDs become apparent when the data block is big enough, that is, when the request is so big that the controller can split it up into portions for the drives to process those portions simultaneously. Mirror arrays don’t act very well here. When the data block size is over 32K, the read speed suddenly degenerates! Probably, the TwinStor technology brings about this effect… Well, we should confess that this technology is not always good.

As you remember, the main discrepancy between 3ware 8506-8 Escalade and 8500-8 Escalade controllers is the support of PCI 64/66MHz, so the results of the four-disk RAID0 and RAID5 are most interesting. Really, comparing the results with those of the 3ware 8500-8 Escalade, we notice that the maximum read speed of the RAID0 array is now 203.5MB/s against those 180.2MB/s that we squeezed out of the Escalade 8500.

The read speed of the RAID5 array is 141.6MB/s with the Escalade 8506 – higher than the 115.2MB/s speed with the Escalade 8500.

Anyway, even the higher performance of the controller chip is not enough for the four-disk RAID0 to be as fast as the quadrupled speed of the single drive.

Now let’s see how the controller behaves in the WriteThrough mode and compare it to the results we’ve just seen:

The difference in the results is negligible when there are no write requests. The status of lazy write doesn’t practically affect the speed of sequential reading.