Software raid rules!

Sigbjorn Strommen sigbjorn.strommen at roxar.com
Thu Apr 18 04:29:00 CDT 2002


Three weeks ago I finally received two Adaptec 39160 SCSI cards
(for a PE2500).

So I've replaced the two megaraid cards (PERC3 DC), as well as
setting the internal aacraid card (PERC3 Di) to operate in SCSI mode.

I then reinstalled RH72/2.4.9-31, setting up the two system disks
in software raid 1, two 73GB internal disks in sw raid 0, and
the twenty 73GB disks (in two PV210s enclosures) in four raid 5
volumes (five disks in each, and each volume on one scsi channel).

In other words, the same raid config as before, but with software
raid instead of hardware raid.


H A L L E L U J A H! 

The performance is so much better I can hardly believe it!
(I got block read speeds of from 150-170MB/s!) The numbers were
so good that I did a rerun of all the tests, doubling the data size
to 4GB, as the server has 1GB RAM, and then I got block reads of
about 125-148MB/s


This is more then 4 times faster then hw raid!  Block write speed
has increased with about 20-30 MB/s, now I get 60-70MB/s.
Rewrite speed is almost tripled, to 37MB/s



For the fun of it I did a stress test, running 8 bonnie sessions in
parallel (1 session for each of the partitions on all the raid 5 volumes),
and even then I get better block read speed for each process then
single runs with hw raid...


Last night I compiled a smaller version of Red Hats 2.4.18-0.22, and
with this kernel I get even better numbers (just a little though).


Another big advantage is that deactivating the aacraid card (using
it in scsi mode) - kernel upgrades runs much more smoothly, no more
struggling to get the system partitions recognized at boot time.




So...finally it seems I can put this server in full production. (I only
hope that it also will be stable with sw raid, and with this kernel!)


A big thanks to all of you who persuaded me to replace the raid
controllers with SCSI software raid!





-Sigbjorn




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