On Wed, Apr 06, 2005 at 04:52:24PM +0100, Ian Jackson wrote:
> Package: lvm10
> Version: 1.0.4-5woody2 (source)
>
> I have a backup system that makes snapshots of the filesystems when
> backing them up. In order to minimise the risk of snapshots
> overflowing, I arranged for the snapshot to use all of the free space
> in the volume group (since it wasn't being sued for anything else).
>
> However, I was foiled by this test:
>
> if ( size > lv->lv_size * 1.1) {
> fprintf ( stderr, "%s -- ERROR: size of snapshot is too large\n",
> cmd);
> return LVM_EINVALID_CMD_LINE;
>
> This is documented nowhere that I could find. The restriction should
> be removed, silently enforced, or perhaps documented. The error
> message is very unhelpful too.
There's no point in creating a snapshot any bigger! The COW mechanism copies
blocks from the original device into the snapshot as they get changed, but once
it's copied all the blocks once there is nothing else to use the space. the 100%
restriction is just there to stop you wasting disk space. the 10% extra is to
cover metadata.
--
patrick
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