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Subject: Re: New to PostgreSQL, performance considerations
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Alexander Staubo wrote:

> No, fsync=on. The tps values are similarly unstable with fsync=off,  
> though -- I'm seeing bursts of high tps values followed by low-tps  
> valleys, a kind of staccato flow indicative of a write caching being  
> filled up and flushed.

Databases with checkpointing typically exhibit this cyclical throughput 
syndrome.
(put another way : this is to be expected and you are correct that it 
indicates buffered
data being flushed to disk periodically).