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* seqential vs random io
@ 2005-05-23 20:58 David Parker <dparker@tazznetworks.com>
0 siblings, 1 reply; 4+ messages in thread
From: David Parker @ 2005-05-23 20:58 UTC (permalink / raw)
To: pgsql-performance
I just got a question from one our QA guys who is configuring a RAID 10
disk that is destined to hold a postgresql database. The disk
configuration procedure is asking him if he wants to optimize for
sequential or random access. My first thought is that random is what we
would want, but then I started wondering if it's not that simple, and my
knowledge of stuff at the hardware level is, well, limited.....
If it were your QA guy, what would you tell him?
- DAP
------------------------------------------------------------------------
----------
David Parker Tazz Networks (401) 709-5130
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: seqential vs random io
@ 2005-05-23 22:23 John A Meinel <john@arbash-meinel.com>
parent: David Parker <dparker@tazznetworks.com>
0 siblings, 1 reply; 4+ messages in thread
From: John A Meinel @ 2005-05-23 22:23 UTC (permalink / raw)
To: David Parker <dparker@tazznetworks.com>; +Cc: pgsql-performance
David Parker wrote:
> I just got a question from one our QA guys who is configuring a RAID 10
> disk that is destined to hold a postgresql database. The disk
> configuration procedure is asking him if he wants to optimize for
> sequential or random access. My first thought is that random is what we
> would want, but then I started wondering if it's not that simple, and my
> knowledge of stuff at the hardware level is, well, limited.....
>
> If it were your QA guy, what would you tell him?
>
> - DAP
Random. Sequential is always pretty fast, it is random that hurts.
The only time I would say sequential is if you were planning on
streaming large files (like iso images) with low load.
But for a DB, even a sequential scan will probably not be that much data.
At least, that's my 2c.
John
=:->
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^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: seqential vs random io
@ 2005-05-23 22:32 Josh Berkus <josh@agliodbs.com>
parent: John A Meinel <john@arbash-meinel.com>
0 siblings, 0 replies; 4+ messages in thread
From: Josh Berkus @ 2005-05-23 22:32 UTC (permalink / raw)
To: John A Meinel <john@arbash-meinel.com>; +Cc: David Parker <dparker@tazznetworks.com>; pgsql-performance
David,
> > I just got a question from one our QA guys who is configuring a RAID 10
> > disk that is destined to hold a postgresql database. The disk
> > configuration procedure is asking him if he wants to optimize for
> > sequential or random access. My first thought is that random is what we
> > would want, but then I started wondering if it's not that simple, and my
> > knowledge of stuff at the hardware level is, well, limited.....
> >
> > If it were your QA guy, what would you tell him?
Depends on the type of database. OLTP or Web == random access. Data
Warehouse == sequential access.
--
--Josh
Josh Berkus
Aglio Database Solutions
San Francisco
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: seqential vs random io
@ 2005-05-23 22:35 Anjan Dave <adave@vantage.com>
0 siblings, 0 replies; 4+ messages in thread
From: Anjan Dave @ 2005-05-23 22:35 UTC (permalink / raw)
To: David Parker <dparker@tazznetworks.com>; pgsql-performance
I would tell him to go for the random, which is what most DBs would be by nature. What you need to understand will be the cache parameters, read/write cache amount, and stripe size, depending on your controller type and whatever it defaults to on these things.
Thanks,
Anjan
-----Original Message-----
From: David Parker [mailto:dparker@tazznetworks.com]
Sent: Mon 5/23/2005 4:58 PM
To: pgsql-performance@postgresql.org
Cc:
Subject: [PERFORM] seqential vs random io
I just got a question from one our QA guys who is configuring a RAID 10 disk that is destined to hold a postgresql database. The disk configuration procedure is asking him if he wants to optimize for sequential or random access. My first thought is that random is what we would want, but then I started wondering if it's not that simple, and my knowledge of stuff at the hardware level is, well, limited.....
If it were your QA guy, what would you tell him?
- DAP
----------------------------------------------------------------------------------
David Parker Tazz Networks (401) 709-5130
^ permalink raw reply [nested|flat] 4+ messages in thread
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2005-05-23 20:58 seqential vs random io David Parker <dparker@tazznetworks.com>
2005-05-23 22:23 ` John A Meinel <john@arbash-meinel.com>
2005-05-23 22:32 ` Josh Berkus <josh@agliodbs.com>
2005-05-23 22:35 Re: seqential vs random io Anjan Dave <adave@vantage.com>
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