Date: Thu, 21 Jan 2016 21:42:48 -0553.75 From: "William A. Mahaffey III" <wam@hiwaay.net> To: freebsd-questions@freebsd.org Subject: Re: ZFS performance help sought Message-ID: <56A1A3EE.3030507@hiwaay.net> In-Reply-To: <20160121205139.GG4538@blisses.org> References: <20160121205139.GG4538@blisses.org>
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On 01/21/16 14:57, Mason Loring Bliss wrote: > Hi all. > > I've bounced back and forth between FreeBSD and Linux, and one of the reasons > why I tend to part with FreeBSD is frustration with ZFS performance. I'm > using my desktop for a couple roles at home. One of the roles is that it > aggregates back-ups from across my machines and gathers them onto a back-up > pool. > > Running FreeBSD, a zfs send/receive from one pool to another makes my system > almost unusably slow and even begins to dig me into swap a little. As a test > a little while back, I capped the ARC at half RAM, but that didn't matter a > bit. I started looking into scheduler tweaking when I decided to take the > path of least resistance and just install Linux instead. ZFS on Linux on > literally the same hardware, dealing with the same pools, handles this same > disk I/O without a hiccough. > > I've moved back to FreeBSD on this box now, and I'd like to resolve this > issue. I don't know if it's a matter of fixing something broken in FreeBSD's > scheduling or tuning ZFS somehow such that it's friendlier. (For what it's > worth, renice'd zfs processes don't make a bit of difference, just as capping > ARC didn't.) > > The box has FreeBSD 10.2, eight gigs of RAM, and I'm dealing with pools 1TB > or smaller. No deduplication. I'm not enough of a ZFS guru to have a strong > notion of what needs to change. I've not seen anything that seems > particularly relevant in tuning guides. I have precious little diagnostic > data to share. That said, here's a quick idea of what FreeBSD is doing, > captured last night, with my box doing precious little else beyond the > transfer: > > last pid: 2631; load averages: 9.44, 8.94, 7.28 up 0+00:29:03 22:04:12 > 58 processes: 2 running, 56 sleeping > CPU: 0.8% user, 0.0% nice, 95.8% system, 0.1% interrupt, 3.3% idle > Mem: 136M Active, 14M Inact, 6915M Wired, 8784K Cache, 855M Free > ARC: 6234M Total, 248M MFU, 5233M MRU, 626M Anon, 45M Header, 82M Other > Swap: 8192M Total, 884K Used, 8191M Free > > PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND > 1334 root 1 52 15 42248K 3164K RUN 0 1:27 7.57% zfs > 1333 root 1 38 15 42248K 3232K pipewr 1 1:04 4.98% zfs > > Not that this matters in grand scheme of things, but I'm hoping to get a > handle on what's happening here before frustration drives me back to Linux. > I'd be happy to gather diagnostics given some pointers on what would be > useful. It seems unlikely that FreeBSD is this desperately inferior to Linux > in terms of the competency of its scheduler, but I'm not sure what to tune to > bring it up to the generally usable state I see on the same hardware under > Linux. > > Thanks in advance! What version of Linux, if you don't mind ? TIA & have a good one. -- William A. Mahaffey III ---------------------------------------------------------------------- "The M1 Garand is without doubt the finest implement of war ever devised by man." -- Gen. George S. Patton Jr.
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