From: Luke Lonergan <llonergan@greenplum.com>
To: PFC <lists@peufeu.com>
To: Jeffrey W. Baker <jwbaker@acm.org>
To: pgsql-performance@postgresql.org
Subject: Re: Huge Data sets, simple queries
Date: Tue, 31 Jan 2006 15:13:10 -0800
Message-ID: <C0052F06.1B638%llonergan@greenplum.com> (raw)
In-Reply-To: <op.s39morhucigqcu@apollo13>
PFC,
On 1/31/06 3:11 PM, "PFC" <lists@peufeu.com> wrote:
>> ... Prove it.
>>
>
> (I have a software RAID1 on this desktop machine)
>
> It's a lot faster than a single disk for random reads when more than 1
> thread hits the disk, because it distributes reads to both disks. Thus,
> applications start faster, and the machine is more reactive even when the
> disk is thrashing. Cron starting a "updatedb" is less painful. It's cool
> for desktop use (and of course it's more reliable).
Exactly - improved your random seeks.
> However large reads (dd-style) are just the same speed as 1 drive. I
> guess you'd need a humongous readahead in order to read from both disks.
Nope - won't help.
- Luke
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To: pgsql-performance@postgresql.org
Cc: llonergan@greenplum.com, lists@peufeu.com, jwbaker@acm.org
Subject: Re: Huge Data sets, simple queries
In-Reply-To: <C0052F06.1B638%llonergan@greenplum.com>
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