Re: Something else about Redo Logs disappearing - Mailing list pgsql-general
From | Adrian Klaver |
---|---|
Subject | Re: Something else about Redo Logs disappearing |
Date | |
Msg-id | c5ae78f9-e922-29bc-379d-739baeb06e2f@aklaver.com Whole thread Raw |
In response to | Re: Something else about Redo Logs disappearing (Peter <pmc@citylink.dinoex.sub.org>) |
Responses |
Re: Something else about Redo Logs disappearing
(Tom Lane <tgl@sss.pgh.pa.us>)
Re: Something else about Redo Logs disappearing (Stephen Frost <sfrost@snowman.net>) Re: Something else about Redo Logs disappearing (Peter <pmc@citylink.dinoex.sub.org>) |
List | pgsql-general |
On 6/8/20 7:33 PM, Peter wrote: > > Actually, the affair had some good side: as usual I was checking > my own designs first and looking for flaws, and indeed I found one: > > If you do copy out the archive logs not directly to tape, but to > some disk area for further processing, then there is an issue with > possible loss. If you do it like the docs say, with a command like > this: > > archive_command = 'test ! -f /mnt/server/archivedir/%f && cp %p > +/mnt/server/archivedir/%f' # Unix > > That "cp" is usually not synchronous. So there is the possibility > that this command terminates successfully, and reports exitcode zero > back to the Postgres, and then the Postgres will consider that log > being safely away. Which is why just following the above command in the docs is: "(This is an example, not a recommendation, and might not work on all platforms.) " Generally for peace of mind folks use third party tools like: pg_backrest(https://pgbackrest.org/), pg_probackup(https://postgrespro.com/products/extensions/pg_probackup) or Barman(https://www.pgbarman.org/). as they offer safety checks for your backups. I use pg_backrest, but it does not look promising for running on BSD: https://fluca1978.github.io/2019/03/04/pgbackrest_FreeBSD.html Not sure about pg_probackup. Barman is Python package: http://docs.pgbarman.org/release/2.10/#installation-from-sources > > But the target of the copy may not yet been written to disk. If > at that point a power loss happens, the log may become missing/damaged/ > incomplete, while the database may or may not consider it done > when restarting. > > Therefore, mounting such a target filesystem in all-synchronous mode > might be a good idea. (UFS: "-o sync", ZFS: "set sync=always") > > cheerio, > PMc > > -- Adrian Klaver adrian.klaver@aklaver.com
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