2120S poor performance

Jon Noack noackjr at alumni.rice.edu
Thu Dec 9 10:50:58 PST 2004

Bill Anderson wrote:
> I've got a 3x72g RAID5 array with U320 disks on an Adaptec 2120S
> controller under Freebsd 4.10.  I'm getting about 25MB/s for sequential
> reads/writes (e.g.  dd if=/dev/aacd0s1b of=/dev/null bs=32k).  I've
> turned on write caching for the container (container set cache
> /write_cache_enable) and turned off the read caching, per previous posts
> to this list.  I'm going to try setting hw.aac.iosize_max to 96k tonight
> to see if that helps.  I'm currently using an IDE disk that gets about
> 45MB/s, so I can hardly consider it an "upgrade" to switch to a 25MB/s
> U320 SCSI system.  :/
> I've also read that the 2120S is slow because of its design.  I'm trying
> to figure out whether the performance can be increased significantly (I
> saw a posting of a linux user getting 37.5MB/s, which although still slow
> might be acceptable), or if I'm better off getting a new card.  I'm
> thinking the latter is the case based on previous postings, but since it
> will probably be quite expensive to replace it, I wanted to get some more
> data.
> What performance should I be expecting from a decent U320 RAID5
> controller?
> Has anyone gotten a 2120S to perform above 30Mb/s in FreeBSD?
> What's the cheapest controller that still gives reasonable performance?
> (If you could give a couple different ones, with their associated
> performance (under FreeBSD), or tell me where to find such information,
> that would be great)

The asr driver is in need of a lot of attention.  Still, testing random
read/write is much better than testing sequential i/o as most real-world
workloads aren't sequential in nature.  The raidtest utility (now in
ports) does an excellent job with random read/write testing.

There are many quality, (relatively) cheap controllers out there, but if
you're looking to stick with Adaptec get a 2130S.  The 2130S uses the aac
driver, which is quite well tuned and maintained by Scott Long.


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