> 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.

BTW, effective_cache_size doesn't determine the amount of caching done.  It 
just informs the planner about how much db is likely to be cached.  The 
actual caching is up to the OS/filesystem.


Josh Berkus
Aglio Database Solutions
San Francisco

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