Josh Berkus wrote:
>
> Hmmm. I thought this was pretty clear. There's three levels of synch
> which are useful features:
>
> 1) "synchronus" standby which is really asynchronous, but only has a gap
> of < 100ms.
>
> 2) Synchronous standby which guarentees that all committed transactions
> are on the failover node and that no data will be lost for failover, but
> the failover node is still in standby mode.
>
> 3) Synchronous replication where the standby node has identical
> transactions to the master node, and is queryable read-only.
>
> Any of these levels would be useful....
Isn't the "queryable read-only" feature totally orthogonal with
how synchronous the replication is?
For one reporting system I have, where new data is continually
being added every second; I'd love to have a read-only-slave
even if that system has the "100ms" gap you mentioned in #1.
Heck I don't care if the queries it runs even have a 100 *minute*
gap; but I sure would like it to be synchronous in the sense
that all the transactions to survive a failure of the primary.