Re: Sync Rep: First Thoughts on Code - Mailing list pgsql-hackers

From Josh Berkus
Subject Re: Sync Rep: First Thoughts on Code
Date
Msg-id 4946C6C7.5090001@agliodbs.com
Whole thread Raw
In response to Re: Sync Rep: First Thoughts on Code  (Peter Eisentraut <peter_e@gmx.net>)
Responses Re: Sync Rep: First Thoughts on Code  (Ron Mayer <rm_pg@cheapcomplexdevices.com>)
Re: Sync Rep: First Thoughts on Code  (Simon Riggs <simon@2ndQuadrant.com>)
Re: Sync Rep: First Thoughts on Code  (Markus Wanner <markus@bluegap.ch>)
List pgsql-hackers
Peter Eisentraut wrote:
> Simon Riggs wrote:
>> I am truly lost to understand why the *name* "synchronous replication"
>> causes so much discussion, yet nobody has discussed what they would
>> actually like the software to *do*
> 
> It's the color of the bikeshed ...

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 and allow a certain number of our 
users to deploy PostgreSQL in an environment where it wasn't used 
before.  So if we can only do (2) for 8.4, that's still very useful for 
telecoms and banks.

--Josh



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