aac0: COMMAND 0xffffffffxxxxxxxx TIMEOUT AFTER xx SECONDS
Doug White
dwhite at gumbysoft.com
Fri Jun 9 19:09:41 UTC 2006
On Fri, 9 Jun 2006, Chris Hedley wrote:
> I've been receiving this message quite a lot lately if I put my Adaptec
> 2410SA aac controller under really heavy load. A quick look at the archives
> suggests that it used to be a problem a couple of years ago, but was
> apparently fixed. Personally I've had no bother with it until a few months
> ago when I upgraded my version of -CURRENT, at which point it started
> misbehaving.
I assume you've checked cabling and termination? Frequently, driver
updates can improve performance which means less tolerance for marginal
configurations.
> I'm also wondering if I might not be better off actually replacing the card
> with something better, or at least something better suited to FreeBSD: with
> the discs' and controller's write-caching turned off, the 2410SA is s-l-o-w,
> about 6MB/s for contiguous writes to an array (either RAID-5 or RAID-10)
> (benchmarked using the admittedly somewhat crude "dd various block sizes
> to/from a /dev entry" technique), although reads are acceptable at
> ~50-60MB/s, if not especially earth-shattering. Any suggestions (for
> something inexpensive! If money were no object I'd've gone for a SCSI-only
> system), or might I just as well stick with the 2410SA?
6MB/s sounds like you aren't getting any help from the card's write cache;
its having to do stripe reads to recalculate parity instead of doing full
stripe writes. Many cards disable write-back cache if the battery module
isn't present -- make sure you have one and its working. /dev accesses
also use physio so you don't get any benefit from write combining in the
filesystem layer.
Also, in general, hardware RAID beats PCI RAID, hands down.
--
Doug White | FreeBSD: The Power to Serve
dwhite at gumbysoft.com | www.FreeBSD.org
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