> > I have a beast of a Dell server with the following specifications: > • 4x Xeon E5-4657LV2 (48 cores total) > • 196GB RAM > • 2x SCSI 900GB in RAID1 (for the OS) > • 8x Intel S3500 SSD 240GB in RAID10 > • H710p RAID controller, 1GB cache > Centos 6.6, RAID10 SSDs uses XFS (mkfs.xfs -i size=512 /dev/sdb).
Things to check - disk cache settings (EnDskCache - for SSD should be on or you're going to lose 90% of your performance) - OS settings e.g. echo noop > /sys/block/sda/queue/scheduler echo 975 > /sys/block/sda/queue/nr_requests blockdev --setra 16384 /dev/sdb - OS kernel version We use H710Ps with SSDs as well, and these settings make a measurable difference to our performance here (though we measure more than just pgbench since it's a poor proxy for our use cases). Also - SSDs - is the filesystem aligned and block size chosen correctly (you don't want to be forced to read 2 blocks of SSD to get every data block)? RAID stripe size? May make a small difference. - are the SSDs all sitting on different SATA channels? You don't want them to be forced to share one channel's worth of bandwidth. The H710P has 8 SATA channels I think (?) and you mention 10 devices above. Graeme Bell. On 10 Dec 2014, at 00:28, Strahinja Kustudić <strahin...@nordeus.com> wrote: > I have a beast of a Dell server with the following specifications: > • 4x Xeon E5-4657LV2 (48 cores total) > • 196GB RAM > • 2x SCSI 900GB in RAID1 (for the OS) > • 8x Intel S3500 SSD 240GB in RAID10 > • H710p RAID controller, 1GB cache > Centos 6.6, RAID10 SSDs uses XFS (mkfs.xfs -i size=512 /dev/sdb). > > Here are some relevant postgresql.conf settings: > shared_buffers = 8GB > work_mem = 64MB > maintenance_work_mem = 1GB > synchronous_commit = off > checkpoint_segments = 256 > checkpoint_timeout = 10min > checkpoint_completion_target = 0.9 > seq_page_cost = 1.0 > effective_cache_size = 100GB > > I ran some "fast" pgbench tests with 4, 6 and 8 drives in RAID10 and here are > the results: > > time /usr/pgsql-9.1/bin/pgbench -U postgres -i -s 12000 pgbench # 292GB DB > > 4 drives 6 drives 8 drives > 105 min 98 min 94 min > > /usr/pgsql-9.1/bin/pgbench -U postgres -c 96 -T 600 -N pgbench # Write test > > 4 drives 6 drives 8 drives > 6567 7427 8073 > > /usr/pgsql-9.1/bin/pgbench -U postgres -c 96 -T 600 pgbench # Read/Write test > > 4 drives 6 drives 8 drives > 3651 5474 7203 > > /usr/pgsql-9.1/bin/pgbench -U postgres -c 96 -T 600 -S pgbench # Read test > > 4 drives 6 drives 8 drives > 17628 25482 28698 > > > A few notes: > • I ran these tests only once, so take these number with reserve. I > didn't have the time to run them more times, because I had to test how the > server works with our app and it takes a considerable amount of time to run > them all. > • I wanted to use a bigger scale factor, but there is a bug in pgbench > with big scale factors. > • Postgres 9.1 was chosen, since the app which will run on this server > uses 9.1. > • These tests are with the H710p controller set to write-back (WB) and > with adaptive read ahead (ADRA). I ran a few tests with write-through (WT) > and no read ahead (NORA), but the results were worse. > • All tests were run using 96 clients as recommended on the pgbench > wiki page, but I'm sure I would get better results if I used 48 clients (1 > for each core), which I tried with the R/W test and got 7986 on 8 drives, > which is almost 800TPS better than with 96 clients. > > Since our app is tied to the Postgres performance a lot, I'm currently trying > to optimize it. Do you have any suggestions what Postgres/system settings I > could try to tweak to increase performance? I have a feeling I could get more > performance out of this system. > > > Regards, > Strahinja -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
