Adaptec RAID 3805 8-port SATA and SAS Controller Review

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Sequential Reads

Hdparm is a simple hard drive configuration tool in linux. In the old days its how linux users would activate DMA and manually shut down drives. It also has a couple nice tests that show basic sequential read performance both on the drive itself and its cache. The cache speed is constant so it has been omitted.

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What sticks out here is the raid0 performance. After we got past 4 drives and moved to 6 there was a fairly small difference in read speed. Moving to raid8 actually decreased our read performance mostly likely due to limits of the controller or the 4 lane bus. Getting 350MB/sec on a read is nearly 5x that of a single raptor which tops out at around 67MB/s.

The raid5 performance is fairly consistent as we add more drives. 4 drives yeilds about 135MB/sec which is pretty reasonable for most setups. To gain the performance of a simple Raid0 array however you must jump to 5 or 6 drives.

Raid10 performance was a little suprising. having 4 drives in raid10 is slightly faster than just 2 in raid0. This is likely just some experimental error. The Raid10-8 configuration however does significantly lag behind a straight raid0-4 setup. Apparently writing to all the mirrors swamped the card a bit. The space consumed by raid0-4 and raid10-8 is identical. How important is your data?

Firing up Bonnie++ also shows similar results to the hdparm test. The same slow down from the hdparm test is observed in the raid0-8 configuration. My guess is the controller has reached its processing limit in terms of bandwidth and drive count.

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