21 maj 2014 kl. 22:05 skrev Sean Chittenden <s...@chittenden.org>:
>>>> I did some tests with zfs, and results where appallingly bad, but that was >>>> with db size > ram. >>>>> >>>>> I think the model used by PostgreSQL, as most databases, are very disk >>>>> block centric. Using zfs makes it hard to get good performance. But this >>>>> was some time ago, maybe things have improved. >>> I have some hardware that I ran with last week wherein I was *not* able to >>> reproduce any performance difference between ZFS and UFS2. On both UFS2 and >>> ZFS I was seeing the same performance when using a a RAID10 / set of >>> mirrors. I talked with the Dragonfly folk who originally performed these >>> tests and they also saw the same thing: no real performance difference >>> between ZFS and UFS. I ran my tests on a host with 16 drive, 10K SAS, 192GB >>> RAM. I also created a kernel profiling image and ran the 20 concurrent user >>> test under kgprof(1), dtrace, and pmcstat and have the results available: >>> >>> http://people.freebsd.org/~seanc/pg9.3-fbsd10-profiling/ >>> >>> There are some investigations that are ongoing as a result of these >>> findings. The dfly methodology was observed when generating these results. >>> Stay tuned. -sc >> >> I'm not sure that the ZFS vs UFS2 question is at the core of the >> performance problem. We're definitely seeing marked slowdowns between >> Pg 9.2 and 9.3 on UFS2 (RAID10 + Dell H710p (mfi) raid controller with >> 1GB NVRAM) I never meant that it was the core of our problem. Zfs vs ufs is out of scope here. > > When the working set fits in RAM (OS + PG), there isn't a performance > difference between 9.2 and 9.3. > > This is a good data point. I will try and reproduce this workload and will > run the performance profiling again to see if something else pops up in the > profiling. -sc > I don't agree. My original measurements showed a 20% slowdown for a reasonably small ( <RAM) pgbench database. > -- > Sean Chittenden > s...@chittenden.org > > _______________________________________________ > freebsd-performance@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-performance > To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org" _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org"
