From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.12.11.20060308/8.11.6) with ESMTP id k3PJw5X8004102 for ; Tue, 25 Apr 2006 15:58:05 -0400 Received: from orca.ele.uri.edu (orca.ele.uri.edu [131.128.51.63]) by mx1.redhat.com (8.12.11.20060308/8.12.11) with ESMTP id k3PJw2xV020994 for ; Tue, 25 Apr 2006 15:58:02 -0400 Subject: Re: [linux-lvm] lvm2 *TEMPORARY* PV failure - what happens? From: Ming Zhang In-Reply-To: <444E73C3.7040305@nrel.colostate.edu> References: <444E73C3.7040305@nrel.colostate.edu> Date: Tue, 25 Apr 2006 15:57:29 -0400 Message-Id: <1145995049.26842.103.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Reply-To: mingz@ele.uri.edu, LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii" To: LVM general discussion and development my 2c. fix me if i am wrong either activate the VG partially, and then all LVs on other PVs are still accessible. I remember these LVs will only have RO access. Though I have no idea why. use dm-zero to generate a fake PVs and add to VG, then allow VG to activate and access those LV. But i do not know if you access a LV that is partially or fully on this PV, what will happen. Ming On Tue, 2006-04-25 at 13:08 -0600, Ty! Boyack wrote: > I've been intrigued by the discussion of what happens when a PV fails, > and have begun to wonder what would happen in the case of a transient > failure of a PV. > > The design I'm thinking of is a SAN environment with several > multi-terabyte iSCSI arrays as PVs, being grouped together into a single > VG, and then carving LVs out of that. We plan on using the CLVM tools > to fit into a clustered environment. > > The arrays themselves are robust (RAID 5/6, redundant power supplies, > etc.) and I grant that if we lose the actual array (for example, if > multiple disks fail), then we are in the situation of a true and > possibly total failure of the PV and loss of it's data blocks. > > But there is always the possiblity that we could lose the CPU, memory, > bus, etc. in the iSCSI controller portion of the array, which will cause > downtime, but no true loss of data. Or someone may hit the wrong power > switch and just reboot the thing, taking it offline for a short time. > Yes, that someone would probably be me. Shame on me. > > The key point is that the iSCSI disk will come back in a few > minutes/hours/days depending on the failure type, and all blocks will be > intact when it comes back up. I suppose the analagous situation would > be using LVM on a group of hot swap drives and pulling one of the disks, > waiting a while, and then re-inserting it. > > Can someone please walk me through the resulting steps that would happen > within LVM2 (or a GFS filesystem on top of that LV) in this situation? > > Thanks, > > -Ty! >