Re: [Gnumed-devel] postgresql considerations

[Karsten Hilbert]

> I was wondering what influences GNUmed's performance with regards
> to database performance most.

The proper answer to this question can really only be found by actual
investigation.

Possible reasons are:

- network latency
- many small queries in a use case which would benefit from fewer
  larger queries
- one large queries in a use case which would benefit from many
  smaller queries
- server capability (RAM, disk throughput)
- dark buffers
- wire transmit capacity
- connection setup time (we only ever use one read-only connection
  per thread during app instance lifetime, though, so that would
  only affect write queries)
- missing indices in the database
- unfortunate joins on behalf of the query planner
- unfortunate table layout
- bad statistics of data distribution in the database

> Second questions deals with harddrive performance. I noticed that when
> running 
> Postgresql off an USB thumbdrive that its performance is far worse then an
> old 
> harddrive. I know that USB thumbdrives have poor i/o performance. Is there
> anything to counter this (e.g. getting large chunks of data in one go) ?
> 
> Any explaination is appreciated.

- use a system which makes good use of RAM for write caching
- configure PostgreSQL to not use fsync (but you'll lose ACID)

Karsten

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