Rép. : Re: [HACKERS] Hot Backup
What I understood from the Administrator's guide is:
- Yes, PostgreSQL provides hot backup: it's the pg_dump utility. It'h hot because users can still be connected and work whil pg_dump is running ( though they will be slowed down). ( See Administrator's guide ch9)
- No, PostgreSQL does NOT provide a way to restore a database up to the last commited transaction, with a reapply of the WAL, as Oracle or SQL Server ( and others, I guess) do. That would be a VERY good feature. See Administrator's guide ch11
So, with Pg, if you backup your db every night with pg_dump, and your server crashes during the day, you will loose up to one day of work.
Am I true?
Erwan
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Erwan DUROSELLE // SEAFRANCE DSI
Responsable Bases de Données // Databases Manager
Tel: +33 (0)1 55 31 59 70 // Fax: +33 (0)1 55 31 85 28
email: eduroselle@seafrance.fr
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Neil Conway <neilc@samurai.com> 07/10/2002 19:48 >>>
"Sandeep Chadha" <sandeep@newnetco.com> writes:
Postgresql has been lacking this all along. I've installed postgres
7.3b2 and still don't see any archive's flushed to any other
place. Please let me know how is hot backup procedure implemented in
current 7.3 beta(2) release.
AFAIK no such hot backup feature has been implemented for 7.3 -- you
appear to have been misinformed.
That said, I agree that would be a good feature to have.
Cheers,
Neil
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Neil Conway <neilc@samurai.com> || PGP Key ID: DB3C29FC
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On Tue, Oct 08, 2002 at 12:35:22PM +0200, Erwan DUROSELLE wrote:
What I understood from the Administrator's guide is:
- Yes, PostgreSQL provides hot backup: it's the pg_dump utility. It'h
hot because users can still be connected and work whil pg_dump is running
( though they will be slowed down). ( See Administrator's guide ch9)
Correct.
- No, PostgreSQL does NOT provide a way to restore a database up to the
last commited transaction, with a reapply of the WAL, as Oracle or SQL
Server ( and others, I guess) do. That would be a VERY good feature. See
Administrator's guide ch11
Umm, I thought the whole point of WAL was that if the database crashed, the
WAL would provide the info to replay to the last committed transaction.
http://www.postgresql.org/idocs/index.php?wal.html
... because we know that in the event of a crash we will be able to recover
the database using the log: ...
These docs seem to corrobrate this.
So, with Pg, if you backup your db every night with pg_dump, and your
server crashes during the day, you will loose up to one day of work.
I've never lost any data with postgres, even if it's crashed, even without
WAL.
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Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
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arithmetic and those that can't.
Martijn!
Tuesday, October 08, 2002, 3:45:13 PM, you wrote:
- No, PostgreSQL does NOT provide a way to restore a database up to the
last commited transaction, with a reapply of the WAL, as Oracle or SQL
Server ( and others, I guess) do. That would be a VERY good feature. See
Administrator's guide ch11
MvO> Umm, I thought the whole point of WAL was that if the database crashed, the
MvO> WAL would provide the info to replay to the last committed transaction.
MvO> http://www.postgresql.org/idocs/index.php?wal.html
MvO> ... because we know that in the event of a crash we will be able to recover
MvO> the database using the log: ...
MvO> These docs seem to corrobrate this.
So, with Pg, if you backup your db every night with pg_dump, and your
server crashes during the day, you will loose up to one day of work.
MvO> I've never lost any data with postgres, even if it's crashed, even without
MvO> WAL.
Suppose you made your nightly backup, and then after a day of work
the building where your server is located disappears in flames..
That's it - you lost one day of work (of course, if your dumps where
stored outside that building otherwise you lost everything)..
There is a need in "incremental" backup, which backs up only those
transactions which has been fulfilled after last "full dump" or last
"incremental dump". These backups should be done quite painlessly -
just copy some part of WAL, and should be small enough (compared to
full dump), so they can be done each hour or even more frequently..
I hope sometime PostgreSQL will support that. :-)
Sincerely Yours,
Timur
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