Re: Moving from 32 to 64 bit builds on Solaris

At 1:01 AM -0500 3/10/07, Tom Lane wrote:
>Dan Sugalski <dan(at)sidhe(dot)org> writes:
>> I assume I'll have to do a 64 bit build to use more than a few gig of
>> shared buffers. If I do that, though, am I going to have to do a
>> database dump and reload,
>
>Yes, most likely, because you'll have changed MAXALIGN and therefore the
>data alignment rules.
>
>You should first ask yourself whether you will get any performance
>benefit from having "more than a few gig of shared buffers". If anyone
>has proven such a benefit I haven't seen it.

Possibly it won't. The machine the DB is on sees heavy access to
large files, to the point where parts of the database may get flushed
out of the OS buffer cache. I was working on the (possibly deeply
flawed assumption) that I'd be better off if more of the database was
guaranteed pinned in memory in Postgres' buffer cache -- it wouldn't
necessarily make the peak performance better, but it would make
average performance better, since I'd not have to sometimes hit disk
to read in things that had been evicted from the disk cache.
--
Dan

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