From: | Ragnar Kjørstad <lvm(at)ragnark(dot)vestdata(dot)no> |
---|---|
To: | linux-lvm(at)sistina(dot)com |
Cc: | Postgres Admin List <pgsql-admin(at)postgresql(dot)org>, "Linux-Xfs (E-mail)" <linux-xfs(at)oss(dot)sgi(dot)com> |
Subject: | Re: [linux-lvm] PostgreSQL and file system level backup |
Date: | 2002-11-16 02:10:32 |
Message-ID: | 20021116031032.V17827@vestdata.no |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-admin |
On Fri, Nov 15, 2002 at 04:25:49PM -0500, Murthy Kambhampaty wrote:
> "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?
Yes, it should.
Allthough, some of the postgresql-developers use the term "corrupt
database" of a database where the table-files are inconsistant. That's
generally _always_ the case when the server is running, as the latest
updates are only available in the database-log. That's also the case for
the LVM-snapshot.
This "inconsistancy" will be fixed by log-replay when you start the server
(after restore).
If you want to avoid it, you can:
- shut down databasee
- take snapshot
- start database
- backup from snapshot
There was a long thread on this subject on the postgresql-list a month
or two ago.
--
Ragnar Kjørstad
Big Storage
From | Date | Subject | |
---|---|---|---|
Next Message | Bruce Momjian | 2002-11-16 03:03:32 | Re: Missing data frrom a shutdown |
Previous Message | Murthy Kambhampaty | 2002-11-15 21:25:49 | PostgreSQL and file system level backup |