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* How much memory?
@ 2005-10-27 19:31 PostgreSQL <martin@portant.com>
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From: PostgreSQL @ 2005-10-27 19:31 UTC (permalink / raw)
To: pgsql-performance
Is there a rule-of-thumb for determining the amount of system memory a
database requres (other than "all you can afford")?
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: How much memory?
@ 2005-10-27 22:39 Ron Peacetree <rjpeace@earthlink.net>
0 siblings, 1 reply; 4+ messages in thread
From: Ron Peacetree @ 2005-10-27 22:39 UTC (permalink / raw)
To: PostgreSQL <martin@portant.com>; pgsql-performance
Databases basically come in 4 sizes:
1= The entire DB fits into memory.
2= The performance critical table(s) fit(s) into memory
3= The indexes of the performance critical table(s) fit into memory.
4= Neither the performance critical tables nor their indexes fit into memory.
Performance decreases (exponentially), and development + maintenance cost/difficulty/pain increases (exponentially), as you go down the list.
While it is often not possible to be in class "1" above, do everything you can to be in at least class "3" and do everything you can to avoid class "4".
At ~$75-$150 per GB as of this post, RAM is the cheapest investment you can make in a high perfomance, low hassle DBMS. IWill's and Tyan's 16 DIMM slot mainboards are worth every penny.
ron
-----Original Message-----
From: PostgreSQL <martin@portant.com>
Sent: Oct 27, 2005 3:31 PM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] How much memory?
Is there a rule-of-thumb for determining the amount of system memory a
database requres (other than "all you can afford")?
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: How much memory?
@ 2005-10-27 22:55 Jim C. Nasby <jnasby@pervasive.com>
parent: Ron Peacetree <rjpeace@earthlink.net>
0 siblings, 1 reply; 4+ messages in thread
From: Jim C. Nasby @ 2005-10-27 22:55 UTC (permalink / raw)
To: Ron Peacetree <rjpeace@earthlink.net>; +Cc: PostgreSQL <martin@portant.com>; pgsql-performance
On Thu, Oct 27, 2005 at 06:39:33PM -0400, Ron Peacetree wrote:
> Databases basically come in 4 sizes:
>
> 1= The entire DB fits into memory.
> 2= The performance critical table(s) fit(s) into memory
> 3= The indexes of the performance critical table(s) fit into memory.
> 4= Neither the performance critical tables nor their indexes fit into memory.
>
> Performance decreases (exponentially), and development + maintenance cost/difficulty/pain increases (exponentially), as you go down the list.
>
> While it is often not possible to be in class "1" above, do everything you can to be in at least class "3" and do everything you can to avoid class "4".
>
> At ~$75-$150 per GB as of this post, RAM is the cheapest investment you can make in a high perfomance, low hassle DBMS. IWill's and Tyan's 16 DIMM slot mainboards are worth every penny.
And note that your next investment after RAM should be better disk IO.
More CPUs *generally* don't buy you much (if anything). My rule of
thumb: the only time your database should be CPU-bound is if you've got
a bad design*.
*NOTE: before everyone goes off about query parallelism and big
in-memory sorts and what-not, keep in mind I said "rule of thumb". :)
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: How much memory?
@ 2005-10-28 14:02 Alex Turner <armtuk@gmail.com>
parent: Jim C. Nasby <jnasby@pervasive.com>
0 siblings, 0 replies; 4+ messages in thread
From: Alex Turner @ 2005-10-28 14:02 UTC (permalink / raw)
To: Jim C. Nasby <jnasby@pervasive.com>; +Cc: Ron Peacetree <rjpeace@earthlink.net>; PostgreSQL <martin@portant.com>; pgsql-performance
Reasons not to buy from Sun or Compaq - why get Opteron 252 when a 240
will do just fine for a fraction of the cost, which of course they
don't stock, white box all the way baby ;). My box from Sun or Compaq
or IBM is 2x the whitebox cost because you can't buy apples to apples.
We have a bitchin' DB server for $7.5k
Alex
On 10/27/05, Jim C. Nasby <jnasby@pervasive.com> wrote:
> On Thu, Oct 27, 2005 at 06:39:33PM -0400, Ron Peacetree wrote:
> > Databases basically come in 4 sizes:
> >
> > 1= The entire DB fits into memory.
> > 2= The performance critical table(s) fit(s) into memory
> > 3= The indexes of the performance critical table(s) fit into memory.
> > 4= Neither the performance critical tables nor their indexes fit into memory.
> >
> > Performance decreases (exponentially), and development + maintenance cost/difficulty/pain increases (exponentially), as you go down the list.
> >
> > While it is often not possible to be in class "1" above, do everything you can to be in at least class "3" and do everything you can to avoid class "4".
> >
> > At ~$75-$150 per GB as of this post, RAM is the cheapest investment you can make in a high perfomance, low hassle DBMS. IWill's and Tyan's 16 DIMM slot mainboards are worth every penny.
>
> And note that your next investment after RAM should be better disk IO.
> More CPUs *generally* don't buy you much (if anything). My rule of
> thumb: the only time your database should be CPU-bound is if you've got
> a bad design*.
>
> *NOTE: before everyone goes off about query parallelism and big
> in-memory sorts and what-not, keep in mind I said "rule of thumb". :)
> --
> Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
> Pervasive Software http://pervasive.com work: 512-231-6117
> vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
>
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2005-10-27 19:31 How much memory? PostgreSQL <martin@portant.com>
2005-10-27 22:39 Re: How much memory? Ron Peacetree <rjpeace@earthlink.net>
2005-10-27 22:55 ` Jim C. Nasby <jnasby@pervasive.com>
2005-10-28 14:02 ` Alex Turner <armtuk@gmail.com>
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