> -----Mensaje original----- > De: Matthew Wakeling [mailto:matthew@xxxxxxxxxxx] > Enviado el: Viernes, 15 de Enero de 2010 08:21 > Para: Scott Marlowe > CC: Fernando Hevia; pgsql-performance@xxxxxxxxxxxxxx > Asunto: Re: new server I/O setup > > On Thu, 14 Jan 2010, Scott Marlowe wrote: > >> 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 > >> > >> 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 > > > > 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. > > The benefits of splitting off a couple of discs for WAL are > dubious given the BBU cache, given that the cache will > convert the frequent fsyncs to sequential writes anyway. My > advice would be to test the difference. If the bottleneck is > random writes on the 12-disc array, then it may actually help > more to improve that to a 14-disc array instead. I am new to the BBU cache benefit and I have a lot to experience and learn. Hopefully I will have the time to tests both setups. I was wondering if disabling the bbu cache on the RAID 1 array would make any difference. All 256MB would be available for the random I/O on the RAID 10. > > I'd also question whether you need two hot spares, with > RAID-10. Obviously that's a judgement call only you can make, > but you could consider whether it is sufficient to just have > a spare disc sitting on a shelf next to the server rather > than using up a slot in the server. Depends on how quickly > you can get to the server on failure, and how important the data is. > This is something I havent been able to make my mind since its very painful to loose those 2 slots. They could make for the dedicated pg_xlog RAID 1 Greg's suggesting. Very tempting, but still think I will start safe for know and see what happens later. Thanks for your hindsight. Regards, Fernando. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
