Re: WAL and master multi-slave replication

Eduardo Morras escribió:
> At 19:25 24/06/2009, you wrote:
>> On Wed, Jun 24, 2009 at 11:22 AM, Eduardo Morras<emorras(at)s21sec(dot)com> wrote:
>> > Yes, there will be 3 masters recolleting data (doing updates, inserts and
>> > deletes) for now and 5 slaves where we will do the searches. The
>> slaves must
>> > have all the data recollected by the 3 masters and the system must be
>> easily
>> > upgradable, adding new masters and new slaves.
>>
>> You know you can't push WAL files from > 1 server into a slave, right?
>
> No, i didn't know that.

I guess you don't know either that you can't query a slave while it is
on recovery (so it's only a "warm" standby, not hot). And if you bring
it up you can't afterwards continue applying more segments later.

What you can do is grab a filesystem snapshot before bringing it online,
and then restoring that snapshot when you want to apply some more
segments to bring it up to date (so from Postgres' point of view it
seems like it was never brought up in the first place).

--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support