Re: Huge Data sets, simple queries

From: PFC <lists(at)peufeu(dot)com>
To: "Luke Lonergan" <llonergan(at)greenplum(dot)com>, "Jeffrey W(dot) Baker" <jwbaker(at)acm(dot)org>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Huge Data sets, simple queries
Date: 2006-01-31 23:11:05
Message-ID: op.s39morhucigqcu@apollo13
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-performance


>> Linux does balanced reads on software
>> mirrors. I'm not sure why you think this can't improve bandwidth. It
>> does improve streaming bandwidth as long as the platter STR is more than
>> the bus STR.
>
> ... 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).

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.

In response to

Responses

Browse pgsql-performance by date

  From Date Subject
Next Message Jim C. Nasby 2006-01-31 23:12:27 Re: Huge Data sets, simple queries
Previous Message Luke Lonergan 2006-01-31 22:52:57 Re: Huge Data sets, simple queries