Anjan,

> Pretty soon, a PowerEdge 6650 with 4 x 2Ghz XEONs, and 8GB Memory, with
> internal drives on RAID5 will be delivered. Postgres will be from RH8.0.

How many drives?   RAID5 sucks for heavy read-write databases, unless you have 
5+ drives.  Or a large battery-backed cache.

Also, last I checked, you can't address 8GB of RAM without a 64-bit processor.  
Since when are the Xeons 64-bit?

> Shared_buffers (25% of RAM / 8KB)) = 8589934592 * .25 / 8192 = 262144

That's too high.  Cut it in half at least.  Probably down to 5% of available 
RAM.

> Sort_mem (4% of RAM / 1KB) = 335544. We'll take about half of that -
> 167772

Fine if you're running a few-user-large-operation database.  If this is a 
webserver, you want a much, much lower value.

> Effective_cache_size = 262144 (same as shared_buffers - 25%)

Much too low.  Where did you get these calculations, anyway?

> In a generic sense, these are recommended values I found in some
> documents.

Where?  We need to contact the author of the "documents" and tell them to 
correct things.

> joins, orderby, groupby clauses. The web application is based on
> Apache/Resin and hotspot JVM 1.4.0.

You'll need to estimate the memory consumed by Java & Apache to have realistic 
figures to work with.

> Are the above settings ok to begin with? Are there any other parameters
> that I should configure now, or monitor lateron?

No, they're not.  See:
http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html to tune these 
parameters.


-- 
Josh Berkus
Aglio Database Solutions
San Francisco

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