On Thu, Sep 11, 2008 at 06:18:37PM +0100, Matthew Wakeling wrote:
> On Thu, 11 Sep 2008, Laszlo Nagy wrote:
>> So the basic system will reside on a RAID 1 array, created from two SAS
>> disks spinning at 15 000 rpm. I will buy 10 pieces of Seagate Barracuda
>> 320GB SATA (ES 7200) disks for the rest.
>
> That sounds good. Put RAID 1 on the pair, and RAID 1+0 on the rest. It'll
> be pretty good. Put the OS and the WAL on the pair, and the database on the
> large array.
>
> However, one of the biggest things that will improve your performance
> (especially in OLTP) is to use a proper RAID controller with a
> battery-backed-up cache.
>
> Matthew
>
But remember that putting the WAL on a separate drive(set) will only
help if you do not have competing I/O, such as system logging or paging,
going to the same drives. This turns your fast sequential I/O into
random I/O with the accompaning 10x or more performance decrease.
Ken