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Re: Hardware advice

From: "Roman Fail" <rfail(at)posportal(dot)com>
To: "Adam Witney" <awitney(at)sghms(dot)ac(dot)uk>,"scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>,"Adam Witney" <awitney(at)sghms(dot)ac(dot)uk>
Cc: "pgsql-performance" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Hardware advice
Date: 2003-05-30 17:59:51
Message-ID: 9B1C77393DED0D4B9DAA1AA1742942DA3BCBDC@pos_pdc.posportal.com (view raw or flat)
Thread:
Lists: pgsql-performance
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(at)sghms(dot)ac(dot)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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