Performance in Intel IOMeter DataBase Pattern

As you remember, this pattern is used to check how well the controller can cope with a mixed stream of reads and writes for random 8KB data blocks. By changing the share of reads and writes we can evaluate how well the controller driver can sort them out:

Let’s have a look at a more illustrative picture shown on the graphs:

As the number of write requests increases, the HDD starts performing lazy writes more efficiently, therefore you can see RAID 0 array run faster in case of more HDDs involved only when the share of writes grows bigger. During reading, all arrays run equally fast.

The same situation can be observed with mirroring arrays. RAID 10 of four hard drives manages to run twice as fast as RAID 1 of two HDDs only when the share of writes is big enough, because RAID 10 is none other but a pair of RAID 1 arrays combined into a RAIUD 0 type one. Moreover, random writing onto a RAID 0 arrays is always twice faster than onto a single hard disk drive.

With RAID 5 array the situation is not so smooth any more. we have already seen in case of a 3Ware 7850 controller how the RAID 5 array should actually behave. However, in our today’s case we see a somewhat different situation. At first the arrays demonstrated similar performance growth, and as soon as the number of writes increases, the performance starts dropping down equally fast for both arrays (as it should actually be for RAID 5). The three-HDD array demonstrates higher performance than a four-HDD array. In case of small reads share the RAID 5 array of four drives is no faster than the same array of three. Although it should be faster. All in all, this time I came across the whole bunch of strange things…