Re: Virtualization vs. sharing a server

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Ramiro Barreca wrote:

   1. Is there a configuration option we need to consider to share
      this server?


The two main configuration options that impact how much RAM PostgreSQL uses are shared_buffers and work_mem. If the server is shared, you just need to avoid tuning those upwards as far as you would on a dedicated system. The defaults for both are tiny, so unless you've already pushed these upwards a lot you're unlikely to have any issues in an initial deployment.


   1. What is the recomended hardware for a PostgreSQL server that has
      to support between 500 and 1000 simultaneous user connections?
      Is there a whitepaper about this?


The recommendation is "try not to do that". PostgreSQL connections are fairly expensive, and scaling into hundreds of connections on a single system tends to break down due to connection creation/teardown overhead. You should be investigating a connection pooler to put in between the application and the database, limiting the number of connections to something much smaller. PgBouncer is most people's first choice for this scale of database: http://pgfoundry.org/projects/pgbouncer

Once you've gotten past that issue, recommended hardware varies greatly depending on workload. Read vs. write balance? Size of the critical working set in RAM? Size of the database? Peak commit rate? Types of queries executed by the application? It all factors into the decision.

Add in business requirements for reliability and the inevitable vendor preference, you're likely to end up with a stack of possible configurations you could consider to sort through. There is no generic recommendation for larger systems.

--
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@xxxxxxxxxxxxxxx   www.2ndQuadrant.us


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