[linux-lvm] Fun and games with mirroring

tariq wali ganaiwali at gmail.com
Tue May 22 18:39:23 UTC 2012

if I may ask an elementary question please :) I normally take a snapshot on
lvm partition offcourse that contains MySQL data say /data and then mount
it as ro and then use the ancient tar/scp to copy it elsewhere . Could
anyone please correct me if there is a better way to do it ? like can i
take  a snapshot of /data and transfer the entire volume to another system
( i mean duplicate/mirror it ) ?


sometime /data contains data that I really don't need to be in the snapshot
but the way i take snapshot it pretty much creates a mirror .. I have
always wondered how snapshot thing works because when i take snapshot I
continue to use my original /data and continue to do IO on it while
snapshot is mounted :)

On Tue, May 22, 2012 at 11:27 PM, Stuart D Gathman <stuart at bmsi.com> wrote:

> Long ago, Nostradamus foresaw that on 05/22/2012 10:50 AM, Vic would write:
>> p.s. The reason I want to do this with LVM mirrors rather than MD RAID is
>> that this is potentially a very useful way of grabbing a backup snapshot
>> of a machine prior to some risky operation - it allows me to "fork" a
>> machine onto two sets of media. But if it leaves the result unbootable,
>> that's something of a problem...
>>  LVM RAID is mainly used for pvmove at the moment.  LVM has a ways to go
> to match ZFS or AIX in LVM mirroring features.   MD RAID takes a snapshot
> just fine.  Add the mirror with mdadm, sync it, and "fail" the mirror and
> remove it before physically removing the drive.  I can see the issue with
> multiple PVs, however.  There is no atomic way to fail multiple mirrors at
> once.
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*Tariq Wali.*
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