From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [linux-lvm] Alternate Pathing? References: <20000724135818.A26581@mail.sistina.com> <20000724222446.A22101@jadzia.josv.com> From: "Martin K. Petersen" Date: 24 Jul 2000 19:00:47 -0400 In-Reply-To: Jos Visser's message of "Mon, 24 Jul 2000 22:24:47 +0200" Message-ID: MIME-Version: 1.0 Sender: owner-linux-lvm Errors-To: owner-linux-lvm List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jos Visser Cc: Heinz Mauelshagen , Sergey Vichik , linux-lvm@msede.com >>>>> "Jos" == Jos Visser writes: Jos> Alternate pathing depends on the driver being able to decide that Jos> a device probed via a particular controller is exactly the same Jos> device as one that it has already seen through a controller that Jos> has been probed earlier. I think it will be hard to decide on a Jos> unique identifier that works for all types of block devices Jos> (serial number?) Fortunately, (at least in the FC-AL case) most vendors are smart enough to assign UUIDs to their devices. SCSI inquiries also help. Finally, ext2 and XFS also have UUIDs in their superblocks. Hence we have several ways to get hints about the physical setup. It is my intention to feature a pluggable driver scheme depending on the physical device in the other end. Also, some devices require to be poked to initiate failover/failback. Worst case (i.e. with incredibly stupid hardware) people will have to specify the paths manually. -- Martin K. Petersen, Principal Linux Consultant, Linuxcare, Inc. mkp@linuxcare.com, http://www.linuxcare.com/ Linuxcare. Support for the revolution.