Re: most bang for buck with ~ $20,000

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, Aug 09, 2006 at 10:15:27AM -0500, Scott Marlowe wrote:
> Actually, the BIGGEST win comes when you've got battery backed cache on
> your RAID controller.  In fact, I'd spend money on a separate RAID
> controller for xlog with its own cache hitting a simple mirror set
> before I'd spring for more drives on pg_xlog.  The battery backed cache
> on the pg_xlog likely wouldn't need to be big, just there and set to
> write-back.
> 
> Then put all the rest of your cash into disks on a big RAID 10 config,
> and as big of a battery backed cache as you can afford for it and memory
> for the machine.

Actually, my (limited) testing has show than on a good battery-backed
controller, there's no penalty to leaving pg_xlog in with the rest of
PGDATA. This means that the OP could pile all 8 drives into a RAID10,
which would almost certainly do better than 6+2.

Note that some controllers (such as 3ware) need to periodically test the
life of the BBU, and they disable write caching when they do so, which
would tank performance.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@xxxxxxxxxxxxx
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461


[Postgresql General]     [Postgresql PHP]     [PHP Users]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Yosemite]

  Powered by Linux