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Re: Load distributed checkpoint

From: "Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
To: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>, "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Load distributed checkpoint
Date: 2006-12-22 00:24:11
Message-ID: 00cd01c7255f$80d1ea70$19527c0a@OPERAO (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
----- Original Message ----- 
From: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
To: "Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>; "ITAGAKI
Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
> > Yes, I used half the size of RAM as the shared buffers, which is
> > reasonable.  And I cached all the data.

> For pg, half RAM for shared_buffers is too much. The ratio is good
for
> other db software, that does not use the OS cache.

What percentage of RAM is recommended for shared buffers in general?
40%?  30%?  Or, is the general recommendation like "According to the
amount of your data, this much RAM should be left for the kernel
cache.  But tha's the story on Linux.  It may be different for other
OSes."?
Hmm,  if it is so, it sounds hard for system designers/administrators
to judge.




----- Original Message ----- 
From: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
To: "Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>; "ITAGAKI
Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Sent: Thursday, December 21, 2006 11:04 PM
Subject: RE: [HACKERS] Load distributed checkpoint



> > You were running the test on the very memory-depend machine.
> >> shared_buffers = 4GB / The scaling factor is 50, 800MB of data.
> > Thet would be why the patch did not work. I tested it with DBT-2,
10GB of
> > data and 2GB of memory. Storage is always the main part of
performace here,
> > even not in checkpoints.
>
> Yes, I used half the size of RAM as the shared buffers, which is
> reasonable.  And I cached all the data.

For pg, half RAM for shared_buffers is too much. The ratio is good for
other db software, that does not use the OS cache.

Andreas



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