| From: | Greg Smith <gsmith(at)gregsmith(dot)com> |
|---|---|
| To: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Matthew Wakeling <matthew(at)flymine(dot)org>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: raid10 hard disk choice |
| Date: | 2009-05-22 06:59:18 |
| Message-ID: | alpine.GSO.2.01.0905220255340.20560@westnet.com |
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| Lists: | pgsql-performance |
On Thu, 21 May 2009, Scott Marlowe wrote:
> But in a RAID-10 you aggreate pairs like RAID-0, so you could write
> 250(n/2) times per second on 15k where n=4 and 166(n/2) for 10k drives
> where n=8. So 500 versus 664... ? Or am I getting it wrong.
Adding more spindles doesn't improve the fact that the disks can only
commit once per revolution. WAL writes are way too fine grained for them
to get split across stripes to improve the commit rate.
--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
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