Re: How many Cluster database on a single server - Mailing list pgsql-performance

From Scott Marlowe
Subject Re: How many Cluster database on a single server
Date
Msg-id CAOR=d=3CxbT1u-ERSxfHdFx+fuK-FsM-UDdGOgAiwDRy55vsyw@mail.gmail.com
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In response to Re: How many Cluster database on a single server  ("d.davolio@mastertraining.it" <d.davolio@mastertraining.it>)
List pgsql-performance
On Wed, Oct 19, 2011 at 9:02 AM, d.davolio@mastertraining.it
<d.davolio@mastertraining.it> wrote:
> Hi Craig,
> thanks for your reply. I think I need to add some details on my question,
> like why we would need more than one Cluster Database. We are thinking to
> use the Streaming Replica feature to keep in sync a number of little DB
> servers around the net. The replica should happen on one or more centralized
> servers. I didn't tested the replica personally bus as I can see, it syncs
> the whole Cluster DB. So, on the centralized server(s), we will have perfect
> copies of the Cluster Databases.
> We sure need to test this configuration but first of all I was wondering if
> there are known drawbacks.

The problem with having so many clusters on one machine is the shared
memory that each one needs.  Even with a relatively small shared
memory segment of say 16MB, with 100 clusters you're going to be using
1600MB of memory on that machine for shared memory.

You might be better off with one cluster and using slony to replicate
just the parts that need replication.

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