| From: | "Luke Lonergan" <llonergan(at)greenplum(dot)com> |
|---|---|
| To: | "PFC" <lists(at)peufeu(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 23:13:10 |
| Message-ID: | C0052F06.1B638%llonergan@greenplum.com |
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| Lists: | pgsql-performance |
PFC,
On 1/31/06 3:11 PM, "PFC" <lists(at)peufeu(dot)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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