| From: | david(at)lang(dot)hm |
|---|---|
| To: | David Rees <drees76(at)gmail(dot)com> |
| Cc: | Jeff <threshar(at)threshar(dot)is-a-geek(dot)com>, Matthew Wakeling <matthew(at)flymine(dot)org>, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, A B <gentosaker(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: [PERFORMANCE] Buying hardware |
| Date: | 2009-01-27 04:06:09 |
| Message-ID: | alpine.DEB.1.10.0901262001390.16162@asgard.lang.hm |
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| Lists: | pgsql-performance |
On Mon, 26 Jan 2009, David Rees wrote:
> And yes, the more memory you can squeeze into the machine, the better,
> though you'll find that after a certain point, price starts going up
> steeply. Of course, if you only have a 15GB database, once you reach
> 16GB of memory you've pretty much hit the point of diminishing
> returns.
actually, you need more memory than that. besides the data itself you
would want memory for several other things, among them:
1. your OS
2. your indexes
3. you per-request memory allocations (for sorting, etc)
this is highly dependant on your workload (type and number of parallel
requests)
4. 'dead' tuples in your table (that will be cleared by a vaccum, but
haven't been yet)
and probably other things as well.
I don't know how large a database will fit in 16G of ram, but I suspect
it's closer to 8G than 15G.
any experts want to throw out a rule-of-thumb here?
David Lang
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