On Fri, 2008-09-12 at 13:53 +0300, Hannu Krosing wrote:
> 4. Slave keeps copies of removed pages or rows when WAL apply removes
> old versions .
>
> Possible ways to do this
>
> * inside Slave - have some backup store tied to OldestXmin intervals
>
> * variant 1 - have one global store, accessed through shared mem
> * variant 2 - present removed pages to interested backends and
> let them (decide to) keep them
>
> * outside Slave - having file system keep old snapshots as long as
> needed, still must tie to OldestXmin intervals, but most of work done by
> storage layer (SAN or overlay file system).
Possible options for "outside Slave" filesystem snapshooting -
ZFS ( http://en.wikipedia.org/wiki/ZFS ) is very likely usable
Linux LVM + XFS may be usable -
http://arstechnica.com/articles/columns/linux/linux-20041013.ars
Possibly also http://en.wikipedia.org/wiki/Btrfs .
----------------
Hannu
