TIP: RAID5 and the Escalade 8500

[wyvern]

If any of you purchased an Escalade 8500 RAID controller, don't use the hardware RAID ability provided by the controller. Use Linux Software RAID.

Why? Read on...

I have 8 200GB SATA drives hooked up to the controller. I initially let the controller establish and maintain the RAID5 array, operating under the impression that a hardware controller should be able to manage RAID5 faster than the OS. The filesystem I use is reiserfs. I tried running bonnie++ tests on it, and this is what I got:

Read: 65 Mbytes/s
Write: 21 Mbytes/s

After reading online about other user's experiences with the Escalade in general, I dissolved the hardware array and established a Software RAID5 array (chunk size of 32), and re-ran the bonnie++ tests.

Read: 243 Mbytes/s
Write: 91 Mbytes/s



As an aside, I tried differing chunk sizes and got very little difference.

Don't use the 8500's hardware RAID. 'Nuff said.
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ex nihilo nihil fit

[Nietsnie]

I use a 3ware 8506-4lp, in a raid 10 config.

I was also noticing slow I/O performance, so I gave 3ware tech support a call.


Basically, the default min-readahead and max-readahead values are very low.

his suggestion was the following:

echo 128 > /proc/sys/vm/min-readahead
echo 512 > /proc/sys/vm/max-readahead


So far (I haven't finished a bonnie++ yet), I've noticed about 3-fold increase in performance.