thx. any idea why partially activated VGs can only allow read only access to LVs on even good PVs. I think as long we do not do LVM level change like create new/resize/delete LVs, the write access to LVs data should be allowed right? ming On Tue, 2006-04-25 at 16:34 -0500, Jonathan E Brassow wrote: > 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/<sd dev>/device/state > >> > >> and later > >> > >> echo running > /sys/block/<sd dev>/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/ > > > _______________________________________________ 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/
