From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Anderson Subject: Re: Is there a grand plan for FC failover? Date: Thu, 29 Jan 2004 10:31:14 -0800 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20040129183114.GB896@beaverton.ibm.com> References: <3356669BBE90C448AD4645C843E2BF2802C013BE@xbl.ma.emulex.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e32.co.us.ibm.com ([32.97.110.130]:59873 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S266297AbUA2S0Q (ORCPT ); Thu, 29 Jan 2004 13:26:16 -0500 Content-Disposition: inline In-Reply-To: <3356669BBE90C448AD4645C843E2BF2802C013BE@xbl.ma.emulex.com> List-Id: linux-scsi@vger.kernel.org To: "Smart, James" Cc: 'James Bottomley' , "Philip R. Auld" , 'Patrick Mansfield' , Simon Kelley , SCSI Mailing List , dm-devel@sistina.com Smart, James [James.Smart@Emulex.com] wrote: > > > > -----Original Message----- > > From: James Bottomley [mailto:James.Bottomley@SteelEye.com] > > > > On Thu, 2004-01-29 at 09:49, Philip R. Auld wrote: > > > It needs to be known to the pathing layer if you've got > > load balancing. > > > It has to know which path has the reservation and only use that one. > > > > Well, yes, but your multiple active path implementation just collapsed > > back down to single path in the face of reservations, so it would > > probably be better simply to use failover in the face of reservations > > and clustering. > > Why do you imply that you're down to a single path ? With multiple port > devices, and the T10 unclarity on multiport support, simple reservations > didn't bring you down to the single port access you are describing. Some > devices may have implemented it this way, but the standard didn't say they > had to or even that they should. > > And this picture changes significantly with the use of Persistent > Reservations and the use of keys. > It appears you are mixing port and path. If you have multiple paths to a port created by multiple adapters connecting to this port through a bus, fabric, etc. then simple reservations should restrict you to only one path to this port. Is there a device that implements simple reservations and allows multiple initiators access? -andmike -- Michael Anderson andmike@us.ibm.com