From owner-freebsd-fs@freebsd.org Wed Jul 22 20:06:03 2015 Return-Path: Delivered-To: freebsd-fs@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 761659A8D95 for ; Wed, 22 Jul 2015 20:06:03 +0000 (UTC) (envelope-from paul@kraus-haus.org) Received: from mail-qg0-f41.google.com (mail-qg0-f41.google.com [209.85.192.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 343F51931 for ; Wed, 22 Jul 2015 20:06:02 +0000 (UTC) (envelope-from paul@kraus-haus.org) Received: by qgii95 with SMTP id i95so77163332qgi.2 for ; Wed, 22 Jul 2015 13:05:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:content-type:mime-version:subject:from :in-reply-to:date:content-transfer-encoding:message-id:references:to; bh=Wlnr60k9w2HxY2XBwKnGbXnFJw3PLkCv3tTeC8DQOtM=; b=KgHfPm9kdxOn7iCHhm0CWt6BnHhPsupOSbfqFfjMlNLKhr8CdmpMLiU0hPcK60IvEQ XfFYVtQ1hW0swdiiMg2GCHS1xFvro0Mt0qIK8XEYkfNMTde3q5Vrp7IIXpNBaCpVIY/N 51irio+ZJAd0wMNwZkn0KSdo3FD/3EdyWt/ZfKjcG+Zt4jlpYUMun2LzG5zOsjYUMYTJ ofI2z1lsSckB9uTkstiuKGLkT+OCNXe6Hwv7v85fperZ63glt+b62RfjpXaG1DQhd2pt oH802qWAlN3cP7OPYKZmzoby6Y5sbn2Bc2x6Nyel8aTs6gYUCkvhiS9e/rfrxDVrT1Mh +ndA== X-Gm-Message-State: ALoCoQnQIIYEQpH+wM6rKKtku+cxWkF4UeMi/U6ENqWJ/Wm6CUkkQWRxG7zO7yDRl0ocoEvz5gLq X-Received: by 10.55.50.195 with SMTP id y186mr6504751qky.55.1437595210634; Wed, 22 Jul 2015 13:00:10 -0700 (PDT) Received: from [192.168.2.137] (pool-100-4-179-8.albyny.fios.verizon.net. [100.4.179.8]) by smtp.gmail.com with ESMTPSA id 195sm1233504qhr.13.2015.07.22.13.00.08 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 22 Jul 2015 13:00:08 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Subject: Re: Prioritize resilvering priority From: Paul Kraus In-Reply-To: Date: Wed, 22 Jul 2015 16:00:06 -0400 Content-Transfer-Encoding: quoted-printable Message-Id: <96FF6F66-06D3-4CAE-ABE5-C608A9A85F7A@kraus-haus.org> References: <20150722003218.GD41419@in-addr.com> To: FreeBSD Filesystems X-Mailer: Apple Mail (2.1878.6) X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 22 Jul 2015 20:06:03 -0000 On Jul 22, 2015, at 14:52, javocado wrote: > But I do have: > vfs.zfs.vdev.max_pending: 10 (dynamic) > vfs.zfs.scrub_limit: 10 (loader) >=20 > So, I think I would want to lower one or both of these to increase I/O > responsiveness on the system. Correct? How would the 2 play together = in > terms of which to adjust to achieve the best system performance at the > expense of a longer resilver? vfs.zfs.vdev.max_pending is the limit on the number of disk I/O that can = be outstanding for a drive (or, IIRC, in this case a given vdev). There = has been great debate over tuning this one years ago on the zfs list. = The general consensus is that 10 is a good value for modern SATA drives. = When I was running 4 SATA drives behind a port multiplier (not a great = configuration) I tuned this down to 4 to keep from overwhelming the port = multiplier. Tuning it _down_ will reduce overall throughput to a drive. = It does not differentiate between production I/O and scrub / resilver = I/O. This post: = https://forums.freebsd.org/threads/how-to-limit-scrub-bandwidth-vfs-zfs-sc= rub_limit.31628/ Implies that the vfs.zfs.scrub_limit parameter limits the number of = outstanding I/O but just for scrub / resilver operations. I would start = by tuning it down to 5 or so and watch carefully with iostat -x to see = the effect. Note that newer ZFS code addresses the scrub operation starving the rest = of the system from I/O. I have not had a problem on either my FBSD 9 or = 10 systems. -- Paul Kraus paul@kraus-haus.org