* Larry Rosenman (ler@lerctr.org) [030224 13:48]:
>
> --On Monday, February 24, 2003 12:28:03 -0500 Tom Lane <tgl@sss.pgh.pa.us>
> wrote:
>
> >If he's got an accurate snapshot of the WAL files, everything the
> >database has claimed to be committed will be committed. It's the same
> >scenario as a crash.
>
> the netapp facility is called SnapShot.
>
> What happens is that the original blocks of the file are write protected,
> and any changes are put elsewhere. (I don't recall whether it's the new or
> the old blocks that get saved, but it doesn't matter, the effect is the
> same).
>
> The snapshot stuff in Veritas' VxFS is very similar.
>
> It makes a consistent view of the filesystem available for backup.
And just for completeness, this is also available in Linux via LVM
see http://tldp.org/HOWTO/LVM-HOWTO/index.html - it works great out of
the box on RH8 - we have a 2TB NFS/SMB server built on it.
-Brad