On 16.08.2007 08:42, Mikko Partio wrote:
I have a mission to implement a two-node active-passive PostgreSQL cluster.
The databases at the cluster are rather large (hundreds of GB's) which opts
me to consider a shared disk environment. I know this is not natively
supported with PostgreSQL, but I have been investigating the Red Hat Cluster
Suite with GFS. The idea would be that the cluster programs with gfs (and HP
ilo) would make sure that only one postmaster at a time would be able to
access the shared disk, and in case the active node fails the cluster
software would shift the services to the previously passive node. What I'm
pondering here is that is the cluster able to keep the postmasters
synchronized at all times so that the database won't get corrupted.
Is there anyone on the list that has seen such configuration, or, even
better, implemented it themselves? I found a small document by Devrim Gunduz
describing this scenario but it was rather scant on details.
If shared disk is definitely out of the question, the fallback plan would be
to use drbd and linux-ha.
The usual setup is DRBD + Heartbeat, which is fast, simple and proven.
Using a shared disk / SAN has disadvantages, such as single point of
failure, (usually) non-native fencing and (usually) way higher latency.
DRBD does handle a lot of stuff by it self, which you need to take care
yourself with a plain shared device. Using a cluster file system such as
GFS2, OCFS2 or Lustre is a waste of resources, as you can't have
active/active with PostgreSQL anyway.
--
Regards,
Hannes Dorbath
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