Performance in Intel IOMeter DataBase Pattern

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’s driver is at sorting the requests out.

You see the results for the WriteBack mode in the following table:

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

All arrays show similar speeds under linear workload, at the beginning of the graph (Random Read). However, the RAID1 and RAID10 are faster than the others because 3ware controllers use the exclusive TwinStor technology. It is alternating requests between the drives of the mirror couple, depending on which drive will respond faster according to the current position of its read/write heads (the controller determines the position by keeping track of the request history).

The performance of the single drive is going up as there appear more write requests in the queue due to the lazy write algorithms of the drive.

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 RAID1 and RAID10 arrays also speed up, but more slowly. The RAID5 arrays drew a down-sloping graph: write requests impede them greatly. However, when there’s a big share of writes, the controller even increases its pace somewhat – we saw this curious thing in our review of the 3ware 8500-8 Escalade.