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.
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