Re: Online base backup from the hot-standby

On Mon, Oct 24, 2011 at 11:33 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> On 24.10.2011 15:29, Fujii Masao wrote:
>>
>> In your patch, FPW is always WAL-logged at startup even when FPW has
>> not been changed since last shutdown. I don't think that's required.
>> I changed the recovery code so that it keeps track of last FPW indicated
>> by WAL record. Then, at end of startup, if that FPW is equal to FPW
>> specified in postgresql.conf (which means that FPW has not been changed
>> since last shutdown or crash), WAL-logging of FPW is skipped. This change
>> prevents unnecessary WAL-logging. Thought?
>
> One problem with this whole FPW-tracking is that pg_lesslog makes it fail.
> I'm not sure what we need to do about that - maybe just add a warning to the
> docs. But it leaves a bit bad feeling in my mouth. Usually we try to make
> features work orthogonally, without dependencies to other settings. Now this
> feature requires that full_page_writes is turned on in the master, and also
> that you don't use pg_lesslog to compress the WAL segments or your base
> backup might be corrupt. The procedure to take a backup from the standby
> seems more complicated than taking it on the master - there are more steps
> to follow.

Doing it on the master isn't as easy as I'd like it to be, either.

But it's not really clear how to make it simpler.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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