From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Hannu Krosing <hannu(at)skype(dot)net> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Is full_page_writes=off safe in conjunction with PITR? |
Date: | 2006-04-14 21:31:22 |
Message-ID: | 26024.1145050282@sss.pgh.pa.us |
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Hannu Krosing <hannu(at)skype(dot)net> writes:
> hel kenal peval, R, 2006-04-14 kell 16:40, kirjutas Tom Lane:
>> If the backup-taker reads, say, 4K at a time then it's
>> certainly possible that it gets a later version of the second half of a
>> page than it got of the first half. I don't know about you, but I sure
>> don't feel comfortable making assumptions at that level about the
>> behavior of tar or cpio.
>>
>> I fear we still have to disable full_page_writes (force it ON) if
>> XLogArchivingActive is on. Comments?
> Why not just tell the backup-taker to take backups using 8K pages ?
How? (No, I don't think tar's blocksize options control this
necessarily --- those indicate the blocking factor on the *tape*.
And not everyone uses tar anyway.)
Even if this would work for all popular backup programs, it seems
far too fragile: the consequence of forgetting the switch would be
silent data corruption, which you might not notice until the slave
had been in live operation for some time.
regards, tom lane
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