Re: Xeon vs Opteron - second revision - tests and questions

Tom Lane napisał(a):

>Marcin Giedz <marcin(dot)giedz(at)eulerhermes(dot)pl> writes:
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>>However I still can see 'spikey' performance but not as much as before
>>changes. What can I do more to eliminate or smooth these spikes?
>>
>>
>
>The spikes are certainly caused by checkpoints. You can fool with the
>checkpoint timing via checkpoint_segments and checkpoint_timeout.
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>
I didn't mention before but I changed checkpoint_segments to 300 but no
checkpoint_time. Disk space doesn't matter at all ... time to
recovery.... shouldn't be very long (I don't have much experiences with
this as I do online backup every day). Can anyone please tell me what
values of these two parametres are reasonable?

Regards,
Marcin

>Usually people put them as far apart as they can stand (the constraint
>on this is mainly how long you'd like to wait for recovery after a
>system crash, and how much disk space you can spare for WAL logs).
>Increasing the bg_writer parameters can be expected to dampen the spikes
>but not eliminate them completely.
>
> regards, tom lane
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