From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267197AbUBMXlc (ORCPT ); Fri, 13 Feb 2004 18:41:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267203AbUBMXlc (ORCPT ); Fri, 13 Feb 2004 18:41:32 -0500 Received: from e32.co.us.ibm.com ([32.97.110.130]:58513 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S267197AbUBMXl1 (ORCPT ); Fri, 13 Feb 2004 18:41:27 -0500 Date: Fri, 13 Feb 2004 15:46:47 -0800 From: Mike Anderson To: Joe Thornber Cc: Lars Marowsky-Bree , Linux Mailing List , axboe@suse.de Subject: Re: dm core patches Message-ID: <20040213234647.GB948@beaverton.ibm.com> Mail-Followup-To: Joe Thornber , Lars Marowsky-Bree , Linux Mailing List , axboe@suse.de References: <20040210163548.GC27507@reti> <20040211101659.GF3427@marowsky-bree.de> <20040211103541.GW27507@reti> <20040212185145.GY21298@marowsky-bree.de> <20040212201340.GB1898@reti> <20040213151213.GR21298@marowsky-bree.de> <20040213153936.GF15736@reti> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040213153936.GF15736@reti> X-Operating-System: Linux 2.0.32 on an i486 User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Joe Thornber [thornber@redhat.com] wrote: > > You are missing the obvious answer: > > > > - Periodically checking paths is a user-space issue and doesn't belong > > into the kernel. User-space gets to handle this policy. > > Yes, that is obvious, I had wanted to do failback automatically. But > pushing it to userland does allow people to write hardware specific > tests. I'll try it and see what people think. Be careful here. Your failback test packet cannot be a media access type as this could cause volume transition thrashing in some types of storage units so most likely you will use a test unit ready type packet. These small size tests are not very good checks on there own for optical based networks as the laser power needed to send them is really low (newer vertical cavity lasers have reduced these types of failures, but they still happens). Auto failback with heuristics and a credit based model allows the path to be failed back in with a quick ejection and a increasing time interval to start the whole cycle again. This keeps the systems from heading into a failover / failback storm. -andmike -- Michael Anderson andmike@us.ibm.com