Bruno Wolff III wrote:
>On Wed, Jun 30, 2004 at 18:23:08 -0500,
> wespvp@syntegra.com wrote:
>
>
>>What do other sites with mondo databases do?
>>
>>
>
>There have been comments from people using storage systems that they
>can freeze the storage system and get a consistant snap shot of the
>file system. This can be used to do a restore. It will look just like
>postgres crashed when coming back up.
>If you find one of the posts about this in the archives the poster may
>have more details on their storage systems.
>
>
We achieve the same effect with LVM. An rsync on the live set of files
is done to get the majority of files that have changed since the last
snapshot, then an LVM snapshot is taken and the relatively small set of
files that have changed are rsyncd. This minimizes the lifetime of the
snapshot. LVM snapshots degrade write performance on the LVM volume
group on which they reside, due to the dual-write they require, so we
want them around for as short a time as possible.
Of course, we also tar up the files after the snapshot rsync, in case
the primary server craps out in the middle of the next hour's
snapshot/rsync. Otherwise, we might find ourselves resorting to last
night's pg_dump.
Regards,
Bill Montgomery