A few months ago a couple guys got "bragging rights" for having the most separate databases. A couple guys claimed several hundred databases and one said he had several thousand databases. The concensus was that Postgres has no problem handling many separate databases.

I took that to heart and redesigned our system; we now have about 150 "primary data sources" that are used to build couple of "warehouses" that our customers actually search. Each database has about 20 tables. The total size (all databases and all tables together) is not huge, about 40 million rows. Eventually the warehouse (customer accessible) databases will be moved to separate servers, configured and indexed specifically for the task.

The only problem I've encountered is messages in the log:

NOTICE: number of page slots needed (131904) exceeds max_fsm_pages (100000)
HINT: Consider increasing the configuration parameter "max_fsm_pages" to a value over 131904.

So I dutifully followed this advice:

max_fsm_pages = 320000
max_fsm_relations = 20000

This is based on our current 150 databases times 20 tables, or 3000 tables total. But I wasn't sure if sequences count as "relations", which would double the number. So I set it at 20K relations to allow for growth.

Is there anything else I need to worry about? What happens if I go to, say, 500 databases (aside from increasing the FSM numbers even more)? 1000 databases?

The servers are 4 GB, dual Xeon, Postgres 8.1.4 on Linux FC4.

Thanks,
Craig


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Craig A. James wrote:

> This is based on our current 150 databases times 20 tables, or 3000 tables
> total. But I wasn't sure if sequences count as "relations", which would
> double the number.

They don't because they don't have free space.

--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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On Wed, Nov 15, 2006 at 02:31:45PM -0300, Alvaro Herrera wrote:
>> This is based on our current 150 databases times 20 tables, or 3000 tables
>> total. But I wasn't sure if sequences count as "relations", which would
>> double the number.
> They don't because they don't have free space.

OTOH, indexes do.

/* Steinar */
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Homepage: http://www.sesse.net/

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