From mboxrd@z Thu Jan 1 00:00:00 1970 Mime-Version: 1.0 (Apple Message framework v623) In-Reply-To: <1145997578.26842.119.camel@localhost.localdomain> References: <444E73C3.7040305@nrel.colostate.edu> <1145995049.26842.103.camel@localhost.localdomain> <1145997578.26842.119.camel@localhost.localdomain> Message-Id: <170c7e6afcd3f12b930f700dc856034e@redhat.com> Content-Transfer-Encoding: 7bit From: Jonathan E Brassow Subject: Re: [linux-lvm] lvm2 *TEMPORARY* PV failure - what happens? Date: Tue, 25 Apr 2006 16:34:21 -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 , mingz@ele.uri.edu y, sounds right. It's pretty much what I get. brassow On Apr 25, 2006, at 3:39 PM, Ming Zhang wrote: > assume 2 scenarios > > 1) this PV is under use when it is disconnected temporarily. then > eventually will return r/w errors to applications. but other LVs are > still accessible. > > 2) system is off and boot up again. for this system will complain PV > with UUID ... is not found. so the only way is to partially activate > VG. > > am i correct here? > > ming > > > > On Tue, 2006-04-25 at 15:21 -0500, Jonathan E Brassow wrote: >> 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/ >>> >> >> _______________________________________________ >> 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/ > > _______________________________________________ > 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/ >