Re: Is full_page_writes=off safe in conjunction with

On Sun, 2006-04-16 at 16:44 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:

> > It seems that we should write an API to allow a backup device to ask for
> > blocks from the database.
> 
> I don't think we have the manpower or interest to develop and maintain
> our own backup tool --- or tools, actually, as you'd at least want a tar
> replacement and an rsync replacement.  Oracle might be able to afford
> to throw programmers at that sort of thing, but where are you going to
> get volunteers for tasks as mind-numbing as maintaining a PG-specific
> tar replacement?

Agreed. The only reason to do that would be to combine it with an
incremental backup solution also, so that some positive benefit also
came from the work.

I think an easier answer must be to make pg_start_backup() throw a
checkpoint, then hold any database writes until pg_stop_backup() is
called. (In the case of full_page_writes = off and fsync = on only).
That way all the data is fsynced to disk and the physical backup is
guaranteed to see whole blocks always, as we need it to. 

--  Simon Riggs EnterpriseDB          http://www.enterprisedb.com/