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Diffstat (limited to 'doc/src/sgml/backup.sgml')
| -rw-r--r-- | doc/src/sgml/backup.sgml | 27 |
1 files changed, 13 insertions, 14 deletions
diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml index f4dc252780b..e8f8b8a5813 100644 --- a/doc/src/sgml/backup.sgml +++ b/doc/src/sgml/backup.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.71 2005/10/15 01:15:33 alvherre Exp $ +$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.72 2005/10/22 21:56:07 tgl Exp $ --> <chapter id="backup"> <title>Backup and Restore</title> @@ -1148,21 +1148,20 @@ restore_command = 'copy /mnt/server/archivedir/%f "%p"' # Windows <para> It should also be noted that the default <acronym>WAL</acronym> - format is fairly bulky since it includes many disk page snapshots. The pages - are partially compressed, using the simple expedient of removing the - empty space (if any) within each block. You can significantly reduce + format is fairly bulky since it includes many disk page snapshots. + These page snapshots are designed to support crash recovery, + since we may need to fix partially-written disk pages. Depending + on your system hardware and software, the risk of partial writes may + be small enough to ignore, in which case you can significantly reduce the total volume of archived logs by turning off page snapshots - using the <xref linkend="guc-full-page-writes"> parameter, - though you should read the notes and warnings in - <xref linkend="reliability"> before you do so. - These page snapshots are designed to allow crash recovery, - since we may need to fix partially-written disk pages. It is not - necessary to store these page copies for PITR operations, however. - If you turn off <xref linkend="guc-full-page-writes">, your PITR - backup and recovery operations will continue to work successfully. + using the <xref linkend="guc-full-page-writes"> parameter. + (Read the notes and warnings in + <xref linkend="reliability"> before you do so.) + Turning off page snapshots does not prevent use of the logs for PITR + operations. An area for future development is to compress archived WAL data by - removing unnecessary page copies when <xref linkend="guc-full-page-writes"> - is turned on. In the meantime, administrators + removing unnecessary page copies even when <varname>full_page_writes</> + is on. In the meantime, administrators may wish to reduce the number of page snapshots included in WAL by increasing the checkpoint interval parameters as much as feasible. </para> |