Re: Mount database on RAM disk?

From: "Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com>
To: <josh(at)agliodbs(dot)com>
Cc: "Stuart Bishop" <stuart(at)stuartbishop(dot)net>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Mount database on RAM disk?
Date: 2005-07-08 19:21:21
Message-ID: 6EE64EF3AB31D5448D0007DD34EEB3415C2CFE@Herge.rcsinc.local
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> Stuart,
>
> > I'm putting together a road map on how our systems can scale as our
load
> > increases. As part of this, I need to look into setting up some fast
> > read only mirrors of our database. We should have more than enough
RAM
> > to fit everything into memory. I would like to find out if I could
> > expect better performance by mounting the database from a RAM disk,
or
> > if I would be better off keeping that RAM free and increasing the
> > effective_cache_size appropriately.
>
> If you're accessing a dedicated, read-only system with a database
small
> enough to fit in RAM, it'll all be cached there anyway, at least on
Linux
> and BSD. You won't be gaining anything by creating a ramdisk.


ditto windows.

Files cached in memory are slower than reading straight from memory but
not nearly enough to justify reserving memory for your use. In other
words, your O/S is a machine with years and years of engineering
designed best how to dole memory out to caching and various processes.
Why second guess it?

Merlin

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