X-bit labs

3ware 8500 SerialATA RAID Controller Review (page 8)

Category: Storage

by Alexander Yuriev , Nikita Nikolaichev

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

Performance in Intel IOMeter Sequential Read & Write Patterns

We chose the WriteBack option in the controller driver for this pattern, but also checked out some of the arrays in the WriteThrough mode. So, 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 (the correlation of the controller’s data-transfer rate and the data block size) are listed in the following tables:

For easier analysis, we divided 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 drives of the array work simultaneously (in parallel).

The read speed graphs for the “mirror” and RAID5 arrays, which improve their reading speed due to certain optimization algorithms, are not monotonous.

Let’s see how the controller behaves in the WriteThrough mode and compare it to the results we have just seen:

As it might have been expected, the difference in the results is negligible when there are no write requests. Turning deferred write on doesn’t practically affect the shape of the graphs.