From: Grant Grundler <grundler@parisc-linux.org>
To: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
linux-parisc@vger.kernel.org, linux-scsi@vger.kernel.org,
matthew@wil.cx
Subject: Re: sym53c8xx_2 data corruption
Date: Wed, 27 Oct 2010 23:59:22 -0600 [thread overview]
Message-ID: <20101028055922.GE32200@lackof.org> (raw)
In-Reply-To: <alpine.DEB.1.10.1010271803010.18202@artax.karlin.mff.cuni.cz>
On Wed, Oct 27, 2010 at 06:19:32PM +0200, Mikulas Patocka wrote:
...
> Requeuing forever is dangerous anyway, a device returning QUEUE_FULL
> constantly could deadlock the system. Question: is it better to risk a
> deadlock with a broken device or to risk a false timeout under high load?
> --- I don't know --- maybe there are valid cases where the device is
> returning QUEUE_FULL for long time (some raid reconfiguration?) ... do you
> know about them?
This was a problem in multi-initiator SCSI systems and I'm guessing also
an issue for FC SAN. Multiple hosts "compete" for filling the device's
available command slots. If all hosts used available queue_depth
(say 32 commands) and device only supported 64 commands at a time,
then the 65th command from host #3 might get QUEUEFULL status back.
I'm not sure what the difference is to BUSY status. Wikipedia
suggests "QUEUE_FULL" is a hint that the device is already
processing commands from the same initiator.
hth,
grant
next prev parent reply other threads:[~2010-10-28 5:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20101024020337.725094D30@hiauly1.hia.nrc.ca>
2010-10-24 3:03 ` C8000 cpu upgrade problem Mikulas Patocka
2010-10-24 3:43 ` Kyle McMartin
2010-10-26 2:16 ` PA caches (was: C8000 cpu upgrade problem) Mikulas Patocka
2010-10-26 3:04 ` Kyle McMartin
2010-10-26 4:30 ` John David Anglin
2010-10-26 16:02 ` Mikulas Patocka
2010-10-27 1:29 ` John David Anglin
2010-10-27 2:40 ` John David Anglin
2010-10-27 4:50 ` James Bottomley
2010-10-27 8:06 ` Mikulas Patocka
2010-10-27 8:35 ` Mikulas Patocka
2010-10-27 14:18 ` James Bottomley
2010-10-27 14:07 ` James Bottomley
2010-10-27 16:28 ` Mikulas Patocka
2010-10-27 16:35 ` James Bottomley
2010-10-27 16:50 ` Mikulas Patocka
2010-10-27 17:07 ` James Bottomley
2010-10-28 6:04 ` John David Anglin
2010-10-28 16:55 ` James Bottomley
2010-10-27 9:04 ` sym53c8xx_2 data corruption Mikulas Patocka
2010-10-27 14:46 ` James Bottomley
2010-10-27 16:19 ` Mikulas Patocka
2010-10-27 16:37 ` James Bottomley
2010-10-28 5:59 ` Grant Grundler [this message]
2010-12-18 20:13 ` PA caches (was: C8000 cpu upgrade problem) John David Anglin
2010-10-24 4:01 ` C8000 cpu upgrade problem John David Anglin
2010-10-26 2:04 ` Mikulas Patocka
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