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Re: cannot mount snapshot

To: Nathan Scott <nathans@xxxxxxx>
Subject: Re: cannot mount snapshot
From: Andi Kleen <ak@xxxxxxx>
Date: Sun, 16 Sep 2001 12:20:00 +0200
Cc: ASANO Masahiro <masano@xxxxxxxxxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <20010914111429.E410868@xxxxxxxxxxxxxxxxxxxxxxxx>; from nathans@xxxxxxx on Fri, Sep 14, 2001 at 11:14:30AM +1100
References: <20010913224933W.masano@xxxxxxxxxxxxxx> <20010914111429.E410868@xxxxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
User-agent: Mutt/1.2.5i
On Fri, Sep 14, 2001 at 11:14:30AM +1100, Nathan Scott wrote:
> In your case, it seems the driver has marked /dev/vg0/masano1
> as readonly (I don't know why that would be - looks like LVM).

LVM snapshots are always read-only unless you add special patches. LVM
only does block COW for writes to the original block device, not for the
snapshot. While it is possible to patch it to do COW for snapshots also
it is probably unsafe (LVM data structures are not journaled etc.) 

To handle such an unpatched LVM xfs_freeze would need to flush the log so 
that no recovery is needed. I actually though it did so already, but it seems
that was mistaken.

-Andi


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