From: Roman Fail <rfail@posportal.com>
To: Adam Witney <awitney@sghms.ac.uk>
To: scott.marlowe <scott.marlowe@ihs.com>
To: Adam Witney <awitney@sghms.ac.uk>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: Hardware advice
Date: Fri, 30 May 2003 10:59:51 -0700
Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA3BCBDC@pos_pdc.posportal.com> (raw)
Based on what you've said, I would guess you are considering the Dell PowerEdge 2650 since it has 5 drive bays. If you could afford the rackspace and just a bit more money, I'd get the tower configuration 2600 with 6 drive bays (and rack rails if needed - Dell even gives you a special rackmount faceplate if you order a tower with rack rails). This would allow you to have this configuration, which I think would be about ideal for the price range you are looking at:
* Linux kernel RAID
* Dual processors - better than a single faster processor, especially with concurrent user load and software RAID on top of that
* 2x36GB in RAID-1 (for OS and WAL)
* 4x146GB in RAID-10 (for data) (alternative: 4-disk RAID-5)
The RAID-10 array gives you the same amount of space you would have with a 3-disk RAID-5 and improved fault tolerance. Although I'm pretty sure your drives won't be hot-swappable with the software RAID - I've never actually had to do it.
I can't say I like Scott's idea much because the WAL and OS are competing for disk time with the data since they are on the same physical disk. In a database that is mainly reads with few writes, this wouldn't be such a problem though.
Just my inexpert opinion,
Roman
-----Original Message-----
From: Adam Witney [mailto:awitney@sghms.ac.uk]
Sent: Fri 5/30/2003 9:55 AM
To: scott.marlowe; Adam Witney
Cc: pgsql-performance
Subject: Re: [PERFORM] Hardware advice
Hi scott,
Thanks for the info
> You might wanna do something like go to all 146 gig drives, put a mirror
> set on the first 20 or so gigs for the OS, and then use the remainder
> (5x120gig or so ) to make your RAID5. The more drives in a RAID5 the
> better, generally, up to about 8 or 12 as the optimal for most setups.
I am not quite sure I understand what you mean here... Do you mean take 20Gb
from each of the 5 drives to setup a 20Gb RAID 1 device? Or just from the
first 2 drives?
Thanks again for your help
adam
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To: pgsql-performance@postgresql.org
Cc: rfail@posportal.com, awitney@sghms.ac.uk, scott.marlowe@ihs.com
Subject: Re: Hardware advice
In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA3BCBDC@pos_pdc.posportal.com>
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