| From: | "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com> |
|---|---|
| To: | Bjoern Metzdorf <bm(at)turtle-entertainment(dot)de> |
| Cc: | <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: [ADMIN] H/W RAID 5 on slower disks versus no raid on |
| Date: | 2002-11-21 21:24:00 |
| Message-ID: | Pine.LNX.4.33.0211211420280.23775-100000@css120.ihs.com |
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| Thread: | |
| Lists: | pgsql-admin pgsql-performance |
On Thu, 21 Nov 2002, Bjoern Metzdorf wrote:
> > In fact, the linux kernel supports >2 drives in a mirror. Useful for a
> > mostly read database that needs to handle lots of concurrent users.
>
> Good to know.
>
> What do you think is faster: 3 drives in raid 1 or 3 drives in raid 5?
Generally RAID 5. RAID 1 is only faster if you are doing a lot of
parellel reads. I.e. you have something like 10 agents reading at the
same time. RAID 5 also works better under parallel load than a single
drive.
The fastest of course, is multidrive RAID0. But there's no redundancy.
Oddly, my testing doesn't show any appreciable performance increase in
linux by layering RAID5 or 1 over RAID0 or vice versa, something that
is usually faster under most setups.
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