>>> Kenneth Marshall <ktm@xxxxxxxx> wrote: > 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. > > 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. Unless you have a good RAID controller with battery-backed-up cache. -Kevin
