I have applied the following patch to document the use of continuous
archiving backups to allow non-simultaneous snapshots.
I don't think we want to go any farther to stop WAL recycling during
back backups.
---------------------------------------------------------------------------
Bruce Momjian wrote:
> Right now it isn't possible to use file system snapshots a reliable
> backup if you are using multiple file systems for tablespaces because
> most systems don't allow the simultaneous snapshoting of multiple file
> system. Our documentation mentions this:
>
> If your database is spread across multiple file systems, there might not
> be any way to obtain exactly-simultaneous frozen snapshots of all the
> volumes. For example, if your data files and WAL log are on different
> disks, or if tablespaces are on different file systems, it might not be
> possible to use snapshot backup because the snapshots must be
> simultaneous. Read your file system documentation very carefully before
> trusting to the consistent-snapshot technique in such situations. The
> safest approach is to shut down the database server for long enough to
> establish all the frozen snapshots.
>
> However, it occurred to me that if someone turned on continuous arciving
> during the file system snapshots, then you could use PITR to recover
> from file system snapshots that were not simultaneous.
>
> Should this be documented?
>
> --
> Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us
> EnterpriseDB http://enterprisedb.com
>
> + If your life is a hard drive, Christ can be your backup. +
>
> --
> Sent via pgsql-hackers mailing list ([email protected])
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--
Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
Index: doc/src/sgml/backup.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/backup.sgml,v
retrieving revision 2.117
diff -c -c -r2.117 backup.sgml
*** doc/src/sgml/backup.sgml 5 Apr 2008 01:34:05 -0000 2.117
--- doc/src/sgml/backup.sgml 9 Apr 2008 02:39:44 -0000
***************
*** 386,394 ****
not be possible to use snapshot backup because the snapshots
<emphasis>must</> be simultaneous.
Read your file system documentation very carefully before trusting
! to the consistent-snapshot technique in such situations. The safest
! approach is to shut down the database server for long enough to
! establish all the frozen snapshots.
</para>
<para>
--- 386,402 ----
not be possible to use snapshot backup because the snapshots
<emphasis>must</> be simultaneous.
Read your file system documentation very carefully before trusting
! to the consistent-snapshot technique in such situations.
! </para>
!
! <para>
! If simultaneous snapshots are not possible, one option is to shut down
! the database server long enough to establish all the frozen snapshots.
! Another option is perform a continuous archiving base backup (<xref
! linkend="backup-base-backup">) because such backups are immune to file
! system changes during the backup. This requires enabling continuous
! archiving just during the backup process; restore is done using
! continuous archive recovery (<xref linkend="backup-pitr-recovery">).
</para>
<para>
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