Re: PITR Functional Design v2 for 7.5

>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