Re: New to PostgreSQL, performance considerations

On Dec 12, 2006, at 13:32 , Michael Stone wrote:

> On Tue, Dec 12, 2006 at 12:29:29PM +0100, Alexander Staubo wrote:
>> I suspect the hardware's real maximum performance of the system
>> is  ~150 tps, but that the LSI's write cache is buffering the
>> writes. I  would love to validate this hypothesis, but I'm not
>> sure how.
>
> With fsync off? The write cache shouldn't really matter in that
> case. (And for this purpose that's probably a reasonable
> configuration.)

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.

Alexander.