From owner-freebsd-questions@freebsd.org Fri Jan 22 00:05:27 2016 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 34964A8AE72 for ; Fri, 22 Jan 2016 00:05:27 +0000 (UTC) (envelope-from mason@blisses.org) Received: from phlegethon.blisses.org (phlegethon.blisses.org [50.56.97.101]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1EB6413CA for ; Fri, 22 Jan 2016 00:05:26 +0000 (UTC) (envelope-from mason@blisses.org) Received: from blisses.org (cocytus.blisses.org [23.25.209.73]) by phlegethon.blisses.org (Postfix) with ESMTPSA id 14C491493BE; Thu, 21 Jan 2016 19:05:25 -0500 (EST) Date: Thu, 21 Jan 2016 19:05:23 -0500 From: Mason Loring Bliss To: dweimer Cc: freebsd-questions@freebsd.org Subject: Re: ZFS performance help sought Message-ID: <20160122000523.GL4538@blisses.org> References: <20160121205139.GG4538@blisses.org> <20160121232810.GJ4538@blisses.org> <20160121235545.GK4538@blisses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160121235545.GK4538@blisses.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 22 Jan 2016 00:05:27 -0000 On Thu, Jan 21, 2016 at 06:55:45PM -0500, Mason Loring Bliss wrote: > Here's what I set: > > vfs.zfs.arc_max="4096M" > vfs.zfs.arc_min="1024M" > vfs.zfs.txg.timeout="3" > vfs.zfs.write_limit_override="512M" > > I'm not seeing any obvious way to verify the write_limit_override setting - > it appears not to show up in sysctl output. > > I'll wait for the current big transfer to finish and then I'll try it with > prefetch disabled too. Disabling prefetch doesn't do a thing here - the system is still painfully overloaded, doing something that was simply unproblematic under Linux. I'd be grateful for further debugging or tuning tips. Is it possible this has nothing to do with ZFS and that I need to play with FreeBSD's scheduling somehow? Again, FreeBSD 10.2, ZFS tuned at noted above, and with prefetch disabled. Eight gigs of RAM, pools less than 1TB. Doing a send/receive between pools on different disks is bringing the system to its knees, where the literal same hardware under Linux/ZoL doesn't break a sweat. What else can I try? -- Mason Loring Bliss (( "In the drowsy dark cave of the mind dreams mason@blisses.org )) build their nest with fragments dropped http://blisses.org/ (( from day's caravan." - Rabindranath Tagore