<div dir="ltr"><div>It all has to do with the write throttle and buffers filling. Here's a great blog post on how it works and how it's tuned: <a href="http://dtrace.org/blogs/ahl/2014/02/10/the-openzfs-write-throttle/">http://dtrace.org/blogs/ahl/2014/02/10/the-openzfs-write-throttle/</a> <a href="http://dtrace.org/blogs/ahl/2014/08/31/openzfs-tuning/">http://dtrace.org/blogs/ahl/2014/08/31/openzfs-tuning/</a> </div>-Chip <div> </div></div><div class="gmail_extra"> <div class="gmail_quote">On Wed, Oct 14, 2015 at 12:45 AM, Rune Tipsmark <<a href="mailto:rt@steait.net" target="_blank">rt@steait.net</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div link="#0563C1" vlink="#954F72" lang="EN-US"> <div> Hi all. Wondering if anyone could shed some light on why my ZFS pool would perform TXG commits up to 5 times per second. It’s set to the default 5 second interval and occasionally it does wait 5 seconds between commits, but only when nearly idle. I’m not sure if this impacts my performance but I would suspect it doesn’t improve it. I force sync on all data. I got 11 mirrors (7200rpm sas disks) two SLOG devices and two L2 ARC devices and a pair of spare disks. Each log device can hold 150GB of data so plenty for 2 TXG commits. The system has 384GB memory. Below is a bit of output from zilstat during a near idle time this morning so you wont see 4-5 commits per second, but during load later today it will happen.. root@zfs10:/tmp# ./zilstat.ksh -M -t -p pool01 txg waiting for txg commit... TIME txg N-MB N-MB/s N-Max-Rate B-MB B-MB/s B-Max-Rate ops <=4kB 4-32kB >=32kB 2015 Oct 14 06:21:19 10872771 3 3 0 21 21 2 234 14 19 201 2015 Oct 14 06:21:22 10872772 10 3 3 70 23 24 806 0 84 725 2015 Oct 14 06:21:24 10872773 12 6 5 56 28 26 682 17 107 558 2015 Oct 14 06:21:25 10872774 13 13 2 75 75 14 651 0 10 641 2015 Oct 14 06:21:25 10872775 0 0 0 0 0 0 1 0 0 1 2015 Oct 14 06:21:26 10872776 11 11 6 53 53 29 645 2 136 507 2015 Oct 14 06:21:30 10872777 11 2 4 81 20 32 873 11 60 804 2015 Oct 14 06:21:30 10872778 0 0 0 0 0 0 1 0 1 0 2015 Oct 14 06:21:31 10872779 12 12 11 56 56 52 631 0 8 623 2015 Oct 14 06:21:33 10872780 11 5 4 74 37 27 858 0 44 814 2015 Oct 14 06:21:36 10872781 14 4 6 79 26 30 977 12 82 883 2015 Oct 14 06:21:39 10872782 11 3 4 78 26 25 957 18 55 884 2015 Oct 14 06:21:43 10872783 13 3 4 80 20 24 930 0 135 795 2015 Oct 14 06:21:46 10872784 13 4 4 81 27 29 965 13 95 857 2015 Oct 14 06:21:49 10872785 11 3 6 80 26 41 1077 12 215 850 2015 Oct 14 06:21:53 10872786 9 3 2 67 22 18 870 1 74 796 2015 Oct 14 06:21:56 10872787 12 3 5 72 18 26 909 17 163 729 2015 Oct 14 06:21:58 10872788 12 6 3 53 26 21 530 0 33 497 2015 Oct 14 06:21:59 10872789 26 26 24 72 72 62 882 12 60 810 2015 Oct 14 06:22:02 10872790 9 3 5 57 19 28 777 0 70 708 2015 Oct 14 06:22:07 10872791 11 2 3 96 24 22 1044 12 46 986 2015 Oct 14 06:22:10 10872792 13 3 4 78 19 22 911 12 38 862 2015 Oct 14 06:22:14 10872793 11 2 4 79 19 26 930 10 94 826 2015 Oct 14 06:22:17 10872794 11 3 5 73 24 26 1054 17 151 886 2015 Oct 14 06:22:17 10872795 0 0 0 0 0 0 2 0 0 2 2015 Oct 14 06:22:18 10872796 40 40 38 78 78 60 707 0 28 680 2015 Oct 14 06:22:22 10872797 10 3 3 66 22 21 937 14 164 759 2015 Oct 14 06:22:25 10872798 9 2 2 66 16 21 821 11 92 718 2015 Oct 14 06:22:28 10872799 24 12 14 80 40 43 750 0 23 727 2015 Oct 14 06:22:28 10872800 0 0 0 0 0 0 2 0 0 2 2015 Oct 14 06:22:29 10872801 15 7 9 49 24 24 526 11 25 490 2015 Oct 14 06:22:33 10872802 10 2 3 79 19 24 939 0 63 876 2015 Oct 14 06:22:36 10872803 10 5 3 59 29 18 756 11 65 682 2015 Oct 14 06:22:36 10872804 0 0 0 0 0 0 0 0 0 0 2015 Oct 14 06:22:36 10872805 13 13 2 58 58 9 500 0 29 471 -- root@zfs10:/tmp# zpool status pool01 pool: pool01 state: ONLINE scan: scrub repaired 0 in 7h53m with 0 errors on Sat Oct 3 06:53:43 2015 config: NAME STATE READ WRITE CKSUM pool01 ONLINE 0 0 0 mirror-0 ONLINE 0 0 0 c4t5000C50055FC9533d0 ONLINE 0 0 0 c4t5000C50055FE6A63d0 ONLINE 0 0 0 mirror-1 ONLINE 0 0 0 c4t5000C5005708296Fd0 ONLINE 0 0 0 c4t5000C5005708351Bd0 ONLINE 0 0 0 mirror-2 ONLINE 0 0 0 c4t5000C500570858EFd0 ONLINE 0 0 0 c4t5000C50057085A6Bd0 ONLINE 0 0 0 mirror-3 ONLINE 0 0 0 c4t5000C50057086307d0 ONLINE 0 0 0 c4t5000C50057086B67d0 ONLINE 0 0 0 mirror-4 ONLINE 0 0 0 c4t5000C500570870D3d0 ONLINE 0 0 0 c4t5000C50057089753d0 ONLINE 0 0 0 mirror-5 ONLINE 0 0 0 c4t5000C500625B7EA7d0 ONLINE 0 0 0 c4t5000C500625B8137d0 ONLINE 0 0 0 mirror-6 ONLINE 0 0 0 c4t5000C500625B8427d0 ONLINE 0 0 0 c4t5000C500625B86E3d0 ONLINE 0 0 0 mirror-7 ONLINE 0 0 0 c4t5000C500625B886Fd0 ONLINE 0 0 0 c4t5000C500625BB773d0 ONLINE 0 0 0 mirror-8 ONLINE 0 0 0 c4t5000C500625BC2C3d0 ONLINE 0 0 0 c4t5000C500625BD3EBd0 ONLINE 0 0 0 mirror-9 ONLINE 0 0 0 c4t5000C50062878C0Bd0 ONLINE 0 0 0 c4t5000C50062878C43d0 ONLINE 0 0 0 mirror-10 ONLINE 0 0 0 c4t5000C50062879687d0 ONLINE 0 0 0 c4t5000C50062879707d0 ONLINE 0 0 0 logs c11d0 ONLINE 0 0 0 c10d0 ONLINE 0 0 0 cache c14d0 ONLINE 0 0 0 c15d0 ONLINE 0 0 0 spares c4t5000C50062879723d0 AVAIL c4t5000C50062879787d0 AVAIL errors: No known data errors Br, Rune </div> </div> _______________________________________________ OmniOS-discuss mailing list <a href="mailto:OmniOS-discuss@lists.omniti.com">OmniOS-discuss@lists.omniti.com</a> <a href="http://lists.omniti.com/mailman/listinfo/omnios-discuss" rel="noreferrer" target="_blank">http://lists.omniti.com/mailman/listinfo/omnios-discuss</a> </blockquote></div> </div>