From: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
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To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
Cc: | Rod Taylor <pg(at)rbt(dot)ca>, "Bort, Paul" <pbort(at)tmwsystems(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Compression and on-disk sorting |
Date: | 2006-05-16 17:31:07 |
Message-ID: | 20060516173107.GH26212@pervasive.com |
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Lists: | pgsql-hackers pgsql-patches |
On Tue, May 16, 2006 at 12:27:42PM -0400, Andrew Dunstan wrote:
> Rod Taylor wrote:
> >>I habitually turn off all compression on my Windows boxes, because it's
> >>a performance hit in my experience. Disk is cheap ...
> >>
> >
> >Disk storage is cheap. Disk bandwidth or throughput is very expensive.
Hey, that's my line! :P
> Sure, but in my experience using Windows File System compression is not
> a win here. Presumably if it were an unqualified win they would have it
> turned on everywhere. The fact that there's an option is a good
> indication that it isn't in many cases. It is most commonly used for
> files like executables that are in effect read-only - but that doesn't
> help us.
The issue with filesystem level compression is that it has to support
things like random access, which isn't needed for on-disk sorting (not
sure about other things like hashing, etc).
In any case, my curiousity is aroused, so I'm currently benchmarking
pgbench on both a compressed and uncompressed $PGDATA/base. I'll also do
some benchmarks with pg_tmp compressed.
Does anyone have time to hack some kind of compression into the on-disk
sort code just to get some benchmark numbers? Unfortunately, doing so is
beyond my meager C abilitiy...
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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