From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Olien Subject: Re: Question about Request Sense case in scsi_lib.c Date: Tue, 12 Oct 2004 09:59:19 -0700 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20041012165919.GA27526@osdl.org> References: <20041012000058.GA26569@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from fw.osdl.org ([65.172.181.6]:16003 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S266221AbUJLQ7W (ORCPT ); Tue, 12 Oct 2004 12:59:22 -0400 Content-Disposition: inline In-Reply-To: List-Id: linux-scsi@vger.kernel.org To: Tim Pepper , linux-scsi@vger.kernel.org Tim, Thanks for the feedback. Yes, Automatic volume transfer is on, and I was expecting there'd be poor performance as a result. I just didn't expect to get IO errors. The odd thing is that the "bus reset" leads to the SCSI request being requeued. But every once in a while, the requeue fails with errors and the request is failed. I'll look at these cases a little more closely, try to understand why the requeues fail. I think the dm multipathing software will soon have hooks to support manual volume transfer in these situations. Dave On Tue, Oct 12, 2004 at 09:29:30AM -0700, Tim Pepper wrote: > I thought on FAStT's while there are dual-active controllers, for a > given lun they weren't active-active, but rather active-passive with > either manual or automatic volume transfer. Assuming automatic volume > transfer is on and you send IOs to both controllers simultaneously you > would ping-pong the cache, drive IO rates lower and possibly see that > manifest itself in interesting behaviour in the linux scsi stack. > With manual volume transfer you should get IO errors from the > controller which is not active or preferred for the given lun. Maybe > somebody involved with their RDAC multipathing driver follows this > list and can comment on their intentions for the 2.6 kernel and dm > multipathing.