On 5/21/09 2:41 PM, "Scott Marlowe" <scott.marlowe@xxxxxxxxx> wrote: > On Thu, May 21, 2009 at 2:29 PM, Robert Haas <robertmhaas@xxxxxxxxx> wrote: >> On Thu, May 21, 2009 at 8:59 AM, Matthew Wakeling <matthew@xxxxxxxxxxx> >> wrote: >>> On Thu, 21 May 2009, Linos wrote: >>>> >>>> i have to buy a new server and in the budget i have (small) i have >>>> to select one of this two options: >>>> >>>> -4 sas 146gb 15k rpm raid10. >>>> -8 sas 146gb 10k rpm raid10. >>> >>> It depends what you are doing. I think in most situations, the second option >>> is better, but there may be a few situations where the reverse is true. >> >> One possible case of this - I believe that 15K drives will allow you >> to commit ~250 times per second (15K/60) vs. ~166 times per second >> (10K/60). If you have a lot of small write transactions, this might >> be an issue. > > But in a RAID-10 you aggreate pairs like RAID-0, so you could write > 250(n/2) times per second on 15k where n=4 and 166(n/2) for 10k drives > where n=8. So 500 versus 664... ? Or am I getting it wrong. >From the original message: " The server would not be only dedicated to postgresql but to be a file server, the rest of options like plenty of ram and battery backed cache raid card are done but this two different hard disk configuration have the same price and i am not sure what it is better." So, with a write-back cache battery backed up raid card, xlog writes won't be an issue. > > -- > Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
