Re: PITR Functional Design v2 for 7.5
От | Simon Riggs |
---|---|
Тема | Re: PITR Functional Design v2 for 7.5 |
Дата | |
Msg-id | 007001c4062c$ba8f7cf0$f3bd87d9@LaptopDellXP обсуждение исходный текст |
Ответ на | Re: PITR Functional Design v2 for 7.5 (Andreas Pflug <pgadmin@pse-consulting.de>) |
Список | pgsql-hackers |
>Andreas Pflug >> Josh Berkus wrote: > >Related to the above, what I don't see in your paper or the proposed API > is a > >way to coordinate full back-ups and WAL archiving. Obviously, the PITR > >Archive is only useful in reference to an existing full backup, so it is > >important to be able to associate a set of PITR archives with a > particular > >full backup, or with some kind of "backup checkpoint". I'm sure that > you > >have a solution for this, I just didn't see it explained in your > proposal, or > >didn't understand it. > > >AFAICS there is a small detail > missing so far. > > When I'm doing a file level hot backup, I can't be sure about the backup > order. To be sure the cluster is in a consistent state regarding > checkpoints, pg_clog must be the first directory backed up. If this > isn't made sure, the situation could arise that the backed up clog > version contains a checkpoint which marks a transaction completed that > has been written to a file which was backed up earlier than the data > write took place. > > This could be insured by doing the backup in two steps; first backing up > pg_clog, and then the rest, restore being performed in the opposite > order. Good spot. I'll add this to the design. Will think more on the "backup checkpoint". Don't let me off the hook... Best Regards, Simon
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