From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [10.15.80.229] (dhcp80-229.msp.redhat.com [10.15.80.229]) by pobox.corp.redhat.com (8.12.8/8.12.8) with ESMTP id k3PKJBIC007162 for ; Tue, 25 Apr 2006 16:19:11 -0400 Mime-Version: 1.0 (Apple Message framework v623) In-Reply-To: <1145995049.26842.103.camel@localhost.localdomain> References: <444E73C3.7040305@nrel.colostate.edu> <1145995049.26842.103.camel@localhost.localdomain> Message-Id: Content-Transfer-Encoding: 7bit From: Jonathan E Brassow Subject: Re: [linux-lvm] lvm2 *TEMPORARY* PV failure - what happens? Date: Tue, 25 Apr 2006 15:21:00 -0500 Reply-To: 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"; format="flowed" To: LVM general discussion and development It is simple to play with this type of scenario by doing: echo offline > /sys/block//device/state and later echo running > /sys/block//device/state I know this doesn't answer your question directly. brassow On Apr 25, 2006, at 2:57 PM, Ming Zhang wrote: > 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! >> > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ >