On Thu, Aug 28, 2008 at 3:29 PM, cluster <skrald@xxxxxxxxxx> wrote: > Thanks for all your replies! They are enlightening. I have some additional > questions: > > 1) Would you prefer > a) 5.4k 2" SATA RAID10 on four disks or > b) 10k 2" SAS RAID1 on two disks? > (Remember the lots (!) of random reads) I'd lean towards 4 disks in RAID-10. Better performance when > 1 read is going on. Similar commit rates to the two 10k drives. Probably bigger drives too, right? Always nice to have room to work in. > 2) Should I just make one large partition of my RAID? Does it matter at all? Probably. With more disks it might be advantageous to split out two drives into RAID-10 for pg_xlog. with 2 or 4 disks, splitting off two for pg_xlog might slow down the data partition more than you gain from a separate pg_xlog drive set. > 3) Will I gain much by putting the OS on a saparate disk, not included in > the RAID? (The webserver and database would still share the RAID - but I > guess the OS will cache my (small) web content in RAM anyway). The real reason you want your OS on a different set of drives is that it allows you to reconfigure your underlying RAID array as needed without having to reinstall the whole OS again. Yeah, logging to /var/log will eat some bandwidth on your RAID as well, but the ease of maintenance is why I do it as much as anything. A lot of large servers support 2 fixed drives for the OS and a lot of removeable drives hooked up to a RAID controller for this reason.
