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

Tom Lane napisał(a):

>Marcin Giedz <marcin.giedz@eulerhermes.pl> writes:
>
>
>>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.
>
>
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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