From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Sipprell Date: Sat, 11 Nov 2000 08:46:02 -0500 Subject: [linux-lvm] LVM in shared parallel SCSI environment Message-ID: <20001111084602.B26544@kevorkian.evcom.net> Mime-Version: 1.0 Content-Disposition: inline Sender: owner-linux-lvm Errors-To: owner-linux-lvm List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-lvm@msede.com Hi all, I'm currently in the process of planning a large(ish)-scale Linux deployment. As part of the planning process, I am considering using LVM in a shared SCSI environment; potentially with GFS as the file system in the future, but starting with ext2. To that end I have a test "cluster" set up. It consists of: One Winchester Systems OpenRAID chassis with 100GB total storage, running in RAID5. The OpenRAID is a SCSI-to-SCSI solution, with four host SCSI channels. The hardware can be configured so that the channels can share physical storage space. Four test Linux boxes, each with a small (9GB) boot/root/swap/emergency SCSI disk. Obviously, the four boxes are connected to the four host channels on the OpenRAID. The OpenRAID is configured such that all available disk space is visable identically to the servers. Obviously, because the initial test uses ext2 instead of a filesystem that supports shared media (i.e. GFS), we won't be actually sharing filesystems between boxes. However, LVM seemed like a pretty good potential in this situation because it allows for relatively dynamic allocation of storage from a large shared "pool." The catch, as with all shared SCSI solutions, is that each participating host must maintain a consistant view of LVM metadata. So far, it's been fairly successful. Once the vg and lvs are created, and each host has meta in core, all is well. The only problem I am seeing is when an lv (for example) is extended or reduced, the other systems are unaware of the change in LVM metadata. This makes sense of course, because each host is operating with it's own "notion" of the LVM in core. The solution is rather awkward; one has to unmount all LVM filesystems on each host, vgchange the vg to inactive, vgchange it back to active and then remount the filesystems. My question is this: Is there any way to "refresh" the in-core metadata from disk? If not, does anyone think this might be a good idea for the future? Regards, -- Jesse Sipprell Technical Operations Director Evolution Communications, Inc. 800.496.4736 * Finger jss@evcom.net for my PGP Public Key *