X-bit labs

3ware 8500 SerialATA RAID Controller Review (page 12)

Category: Storage

by Alexander Yuriev , Nikita Nikolaichev

[ 02/05/2004 | 10:14 PM ]

Performance in Intel IOMeter WorkStation Pattern

Workstation pattern imitates intensive work of a user in various applications in the NTFS5 file system. The table for the WriteBack mode comes first:

And that I the more illustrative graphical representation:

The situation with RAID0 is quite ordinary: the more disks the array has, the faster it processes requests. RAID1 is faster than the single drive even under small workloads, while RAID10 outperforms RAID0 of three disks. RAID5 arrays seem weak against them, but this is actually no surprise. The thing is that numerous random requests for writing small data blocks slow down RAID5 array greatly.

We calculated the performance rating for the WorkStation pattern according to the following formula:

Performance Rating = Total I/O (queue=1)/1 + Total I/O (queue=2)/2 + Total I/O (queue=4)/4 + Total I/O (queue=8)/8 + Total I/O (queue=16)/16 + Total I/O (queue=32)/32.

RAID5 arrays fall behind the single drive. RAID0 arrays lined up in “size order” (according to the number of disks in them), while RAID10 was just a little faster than RAID0 of three disks. RAID1 has a higher performance rating than RAID0 of two disks, although we saw it otherwise in the graphs. That’s because we assume that short queues are more likely to occur in a workstation, therefore, short queues have higher weights in the total result. So, the performance advantage of RAID1 during short queues processing is more than enough to outpace RAID 0 of 2 HDDs in the performance rating chart.

Let’s see how lazy write affects the operation of the arrays in this pattern:

Switching to the WriteThrough mode, the arrays rank up the same way, but perform 25-35% slower (depending on the array type).