On Fri, Mar 9, 2012 at 5:15 AM, Rory Campbell-Lange <rory@xxxxxxxxxxxxxxxxxx> wrote: > I've taken the liberty of reposting this message as my addendum to a > long thread that I started on the subject of adding a new db server to > our existing 4-year old workhorse got lost in discussion. > > Our workload is several small databases totalling less than 40GB of disk > space. The proposed system has 48GB RAM, 2 * quad core E5620 @ 2.40GHz > and 4 WD Raptors behind an LSI SAS card. Our supplier has just run a set > of tests on the machine we intend to buy. The test rig had the following > setup: > > LSI MegaRAID SAS 9260-8i > Firmware: 12.12.0-0090 > Kernel: 2.6.39.4 > Hard disks: 4x WD6000BLHX > Test done on 256GB volume > BS = blocksize in bytes > > The test tool is fio. I'd be grateful to know if the results below are > considered acceptable. An ancillary question is whether a 4096 block > size is a good idea. I suppose we will be using XFS which I understand > has a default block size of 4096 bytes. > > RAID 10 > -------------------------------------- > Read sequential > > BS MB/s IOPs > 512 0129.26 264730.80 > 1024 0229.75 235273.40 > 4096 0363.14 092965.50 > 16384 0475.02 030401.50 > 65536 0472.79 007564.65 > 131072 0428.15 003425.20 > -------------------------------------- > Write sequential > > BS MB/s IOPs > 512 0036.08 073908.00 > 1024 0065.61 067192.60 > 4096 0170.15 043560.40 > 16384 0219.80 014067.57 > 65536 0240.05 003840.91 > 131072 0243.96 001951.74 > -------------------------------------- > Random read > > BS MB/s IOPs > 512 0001.50 003077.20 > 1024 0002.91 002981.40 > 4096 0011.59 002968.30 > 16384 0044.50 002848.28 > 65536 0156.96 002511.41 > 131072 0170.65 001365.25 > -------------------------------------- > Random write > > BS MB/s IOPs > 512 0000.53 001103.60 > 1024 0001.15 001179.20 > 4096 0004.43 001135.30 > 16384 0017.61 001127.56 > 65536 0061.39 000982.39 > 131072 0079.27 000634.16 > -------------------------------------- since your RAM is larger than the database size, read performance is essentially a non-issue. your major gating factors are going to be cpu bound queries and random writes -- 1000 IOPS essentially puts an upper bound on your write TPS, especially if your writes are frequent and randomly distributed, the case that is more or less simulated by pgbench with large scaling factors. Now, 1000 write tps is quite alot (3.6 mil transactions/hour) and your workload will drive the hardware consideration. merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
