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Re: [linux-lvm] Fun and games with mirroring



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 ) ?

Also

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 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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