The postgresql documentation states that in order to get a usable backup from a filesystem dump (or copy) the database server must be shut down. Moreover, "Half-way measures such as disallowing all connections will not work as there is always some buffering going on. For this reason it is also not advisable to trust file systems that claim to support "consistent snapshots"." Just to make certain, is this true with running xfsdump on an LVM snapshot of the XFS filesystem? My question was prompted by a recent post on the linux-xfs list in which one of the xfs maintainers pointed out that xfsdumps are cache coherent. In response to my preliminary question, Tom Lane pointed out that: "Unless the postmaster is shut down meanwhile, you'll probably end up with a corrupt database. The problem is that xfsdump does not give you an instantaneous snapshot of the filesystem state, so you will probably collect inconsistent contents of the various files that make up the database." Which gives rise to my present question: given that LVM DOES give an instantaneous snapshot of the filesystem, would an xfsdump of an LVM snapshot of an XFS filesystem give usable backups? Thanks, Murthy PS: Our databases have crossed the 100 GB size, with some tables reaching 25 GB, so pg_dump is taking more than 5 hours to complete (changing the level of compression in custom format dump files from 6 to 1 did not significantly reduce the dump duration). Otherwise, pg_dump-ing the database (and copying the .conf files) was just dandy. _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
