Re: PostgreSQL user experience: FreeBSD (ZFS) vs OpenIndiana (ZFS) vs Linux (EXT4)
Eduardo Morras <[email protected]>
| Newsgroups | gmane.os.freebsd.performance |
|---|---|
| Message-ID | <[email protected]> |
At 14:26 17/12/2011, you wrote: >Hi everyone, > >I would like to share some of our expreience with PostgreSQL on FreeBSD. >It has been a while ago since we had to stop using FreeBSD for our >customer's PostgreSQL servers. > >PostgreSQL (8.4 and 9.0) was demonstrating slow performance under heavy >loads and one day I decided to compare it to other alternatives on the >very same system (one 8-core with 16GB RAM, another 12-core with 48GB >RAM). With ZFS it was extremely slow and with UFS the speed was >acceptable (still 10-20% slower) if not under high load. Our databases >have a size from several gigabytes to tens of gigabytes. > >A single real-world query on a idle system was noticeably slower on a >FreeBSD system than on the other systems (ZFS and UFS). We compared the >EXPLAIN ANALYZE output and the performance penalty was almost equally >spread on all items. With rising loads, PostgreSQL processes remain a >long time in "semwait" and "msgwait" states and the "top" output shows a >high system load on FreeBSD. > >I have also tried different tunings, compilers and optimizations, but >with that I was able to gain only 5-10% better results. > >The result of a pgbench run by one of my customers on a 12-core system >with 48GB RAM is here (FreeBSD ZFS vs OpenIndiana (ZFS) vs Linux (EXT4): >http://www.vx.sk/benchmarks/postgresql/pgbench_20110630.ods > >So our decision so far is the following: >- if we are building a PostgreSQL server for heavy loads, we prefer >Solaris/OpenIndiana (ZFS or UFS) or Linux (EXT4) to FreeBSD (ZFS or UFS) >- if we want to use PostgreSQL on FreeBSD, we prefer UFS to ZFS > >P.S: Our webservers still run FreeBSD and e.g. OpenIndiana (Solaris) >performed much worse in our high load real-world web application. What FreeBSD tunings have you used in tests? Have you set kern.ipc.shm_use_phys=1? Have you tuned the FreeBSD semaphores? Them increased more than 5-10% on my server, i increased clients from 25 (with saturation problems) to 40 (without problems). About UFS/ZFS, i prefer UFS, it has less memory/cpu footprint that can use for more postgresql cache and tps. >-- >Martin Matuska >FreeBSD committer >http://blog.vx.sk _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "[email protected]"