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Re: [linux-lvm] Duplicate PV's - how does LVM choose which one to use



Long ago, Nostradamus foresaw that on 02/21/2012 11:43 AM, Alasdair G Kergon would write:
On Tue, Feb 21, 2012 at 10:35:03AM -0600, Ray Morris wrote:
Perhaps when duplicates are found the seqno should be incremented
so it DOES use the same one next time, and generate a warning
indicating which one is out of date?
Wouldn't be possible - it can't distinguish between them (or we'd not
be in this situation).

If they have the same UUID it assumes they are different paths to the same
device and picks one of them to use.

But there are other cases (like hardware snapshot, mirror that failed to
start up first) where it's better to stop and force the sysadmin to fix
things.

But if they are different paths, incrementing seqno won't hurt, both paths will see the change. And if it is a mirror that failed to start, then the chosen leg is now distinguishable. Is there a problem with incrementing seqno an extra time at startup when multipath is the normal situation?


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