Re: Replication and PITR

Jeff Davis wrote:
> 8.2 makes PITR much easier to use for the situation you'd like. In 8.1,
> a WAL might sit around for a while before it becomes full and then sent
> off. 8.2 allows you to force a WAL to be sent, and it also allows a
> standby mode.
>
This sounds really neat !

To me this sound like we may be able to replicate using different
priorities, balancing performance and data integrity. But what do you
mean by "standby mode" ? That PG maý be able to serve as a readonly DB
and replication client at the same time ?
> Slony is a good system now, and it's nice because you can use different
> versions of PostgreSQL. PITR requires that it's the same version.
>
The PITR requirement all makes sense, and I don't like the missing DDL
updates and the fact that Slony is trigger.
> However, if you're working with a payment system or accounting system,
> you may need synchronous replication. With any asynchronous solution
> (Slony or PITR standby), there is a possibility (although not likely) to
> lose *committed* transactions.
>
Hmm, yes but again this have to be balanced with performance, and at the
moment I can live with a replication that is a little behind but, I will
try to keep the overhead down.
> If you do need synchronous replication, consider using two-phase commit
> to prepare transactions on several machines before committing them. This
> ensures that the data will be on multiple machines before committing to
> any of them.
>
Hmm, I saw that feature announced in 8.1, and I am sure it will come in
handy one day, but right now async is acceptable.

/BL