Re: aac0: COMMAND 0xffffffffxxxxxxxx TIMEOUT AFTER xx SECONDS

From: Doug White <dwhite_at_gumbysoft.com>
Date: Fri, 9 Jun 2006 12:08:15 -0700 (PDT)
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
Received on Fri Jun 09 2006 - 17:09:41 UTC

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