Re: [Xen-users] A simple backup

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > IMHO, even the best commercial SAN-based backup solution uses that
> > assumption, so for practical purposes, atomic backup for domU's storage
> > should be sufficient.
>
> So are local logical volume snapshots atomic? I could see a network
> block device not being quite atomic with lv snapshot, but it seems that
> local storage on lv should be atomic. I keep reading conflicting data
> about weather it is or is not atomic.

Local LVM snapshots are atomic, I think.  It's just that atomicity of a 
snapshot is not sufficient to guarantee that the snapshot is *consistent*, 
due to caching in the guest.  Yanking the power cord out of the machine 
creates a consistent snapshot of its current disk state (by atomically 
preventing the machine updating its disk ;-)) but that will also need a 
filesystem recovery before the FS is actually readable.

Cheers,
Mark

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