Thanks for all. I change to RAID 1 and here is new pg_bench result: pgbench -h 127.0.0.1 -p 5433 -U postgres -c 10 -T 1800 -s 10 pgbench Scale option ignored, using pgbench_branches table count = 10 starting vacuum...end. transaction type: TPC-B (sort of) scaling factor: 10 query mode: simple number of clients: 10 number of threads: 1 duration: 1800 s number of transactions actually processed: 4373177 tps = 2429.396876 (including connections establishing) tps = 2429.675016 (excluding connections establishing) Press any key to continue . . .
Tuan Hoang ANh On Fri, Dec 23, 2011 at 10:25 PM, Scott Marlowe <scott.marl...@gmail.com>wrote: > On Fri, Dec 23, 2011 at 5:15 AM, alexandre - aldeia digital > <adald...@gmail.com> wrote: > >> I'm not so confident that a RAID-1 will win over a single disk. When it > >> comes to writes, the latency should be ~50 higher (if both disk must > >> sync), since the spindles are not running synchronously. This applies to > >> softraid, not something like a battery-backend raid controller of > course. > >> > >> Or am I wrong here? > >> > > > > Software RAID-1 in Linux, can read data in all disks and generally > increase > > a lot the data rate in reads. In writes, for sure, the overhead is great > > compared with a single disk, but not too much. > > Exactly. Unless you spend a great deal of time writing data out to > the disks, the faster reads will more than make up for a tiny increase > in latency for the writes to the drives. > > As regards the other recommendation in this thread to use two mirror > sets one for xlog and one for everything else, unless you're doing a > lot of writing, it's often still a winner to just run one big 4 disk > RAID-10. > > Of course the real winner is to put a hardware RAID controller with > battery backed cache between your OS and the hard drives, then the > performance of even just a pair of drives in RAID-1 will be quite > fast. > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance >
