Performance in Intel IOMeter DataBase Pattern

Traditionally, we begin by checking the arrays’ ability to process mixed streams of requests.

This pattern is sending a mixed stream of requests to read and write 8KB random-address data blocks. By changing the ratio of reads to writes, we can find out how good the controller driver is at sorting the requests out.

The following table contains the results for the write-through caching mode:

The following diagrams show the dependence of the data-transfer rate on the reads/writes ratio for different request queue depths. For better reading, I drew two diagrams for two groups of arrays:

Under linear workload, almost all the arrays show similar speeds at the beginning of the graph (Random Read mode) and the RAID1 and RAID10 are a little faster than the others. But as the percentage of write requests grows, the RAID1 and RAID10 arrays perform more like the single drive and the two-disk RAID0 and even worse in the Random Write mode (100% writes). FastTRAK S150 SX4 controller seems to be using an algorithm of handling mirror arrays which is similar to TwinStor technology from 3ware. This technology keeps a request history log and determines which drive in the array would process the current request faster. TwinStor brings about an overall advantage in read speed. The maximum performance growth is 15% in this case (in the Random Read mode). By the way, we can recall that the FastTRAK S150 TX4 didn’t alternate requests between the disks of a mirrored couple (see our Promise FastTRAK S150 TX4 Controller Review for details) – so Promise has definitely made some progress in this respect.

The performance of the JBOD array is going up as there appear more write requests in the queue due to the lazy write algorithms of the hard disk drive itself. The speed of the RAID0 grows according to the number of disks in the array, but this proportion is only felt when the percentage of writes is high. The RAID5 arrays are slowing down as the writes percentage grows – write requests slow them down considerably. At the same time, there is no big difference between the speeds of the three- and four-disk RAID5s. That’s rather strange.