On Thu, Jan 14, 2010 at 1:03 PM, Fernando Hevia <fhevia@xxxxxxxxxxxxx> wrote: > Hi all, > > I've just received this new server: > 1 x XEON 5520 Quad Core w/ HT > 8 GB RAM 1066 MHz > 16 x SATA II Seagate Barracuda 7200.12 > 3ware 9650SE w/ 256MB BBU > > It will run an Ubuntu 8.04 LTS Postgres 8.4 dedicated server. Its database > will be getting between 100 and 1000 inserts per second (those are call > detail records of ~300 bytes each) of around 20 clients (voip gateways). > Other activity is mostly read-only and some non time-critical writes > generally at off peak hours. > > So my first choice was: > > 2 discs in RAID 1 for OS + pg_xlog partitioned with ext2. > 12 discs in RAID 10 for postgres data, sole partition with ext3. > 2 spares > > > My second choice is: > > 4 discs in RAID 10 for OS + pg_xlog partitioned with ext2 > 10 discs in RAID 10 for postgres, ext3 > 2 spares. > > The bbu caché will be enabled for both raid volumes. > > I justified my first choice in that WAL writes are sequentially and OS > pretty much are too, so a RAID 1 probably would hold ground against a 12 > disc RAID 10 with random writes. I think your first choice is right. I use the same basic setup with 147G 15k5 SAS seagate drives and the pg_xlog / OS partition is almost never close to the same level of utilization, according to iostat, as the main 12 disk RAID-10 array is. We may have to buy a 16 disk array to keep up with load, and it would be all main data storage, and our pg_xlog main drive pair would be just fine. > I don't know in advance if I will manage to gather enough time to try out > both setups so I wanted to know what you guys think of these 2 > alternatives. Do you think a single RAID 1 will become a bottleneck? Feel > free to suggest a better setup I hadn't considered, it would be most > welcome. For 12 disks, most likely not. Especially since your load is mostly small randomish writes, not a bunch of big multi-megabyte records or anything, so the random access performance on the 12 disk RAID-10 should be your limiting factor. > Pd: any clue if hdparm works to deactive the disks write cache even if they > are behind the 3ware controller? Not sure, but I'm pretty sure the 3ware card already does the right thing and turns off the write caching. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
