[linux-lvm] snapshots and filesystem freezing

Tomasz Chmielewski mangoo at wpkg.org
Fri Feb 8 12:04:46 UTC 2008

Some filesystems, like xfs, have a "freeze" feature. There was a 
discussion on lkml about implementing it in ext3, too.

What is the relationship between a filesystem freeze and LVM snapshots?

As far as I understand, snapshotting a filesystem in any random 
timepoint can mean that the snapshotted fs will be inconsistent (i.e., 
may need fsck).
"Freezing" the filesystem will flush all writes to the media, and a 
snapshotted fs should be consistent then (in theory; without an 
interface between filesystem freeze and LVM snapshot it does not 
guarantee that the operation is "atomic").

Am I correct?

Tomasz Chmielewski

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