From owner-freebsd-questions@FreeBSD.ORG Mon Feb 25 14:19:33 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 0CB1A90 for ; Mon, 25 Feb 2013 14:19:33 +0000 (UTC) (envelope-from paul@kraus-haus.org) Received: from mail-qc0-f182.google.com (mail-qc0-f182.google.com [209.85.216.182]) by mx1.freebsd.org (Postfix) with ESMTP id 9FAAEF27 for ; Mon, 25 Feb 2013 14:19:32 +0000 (UTC) Received: by mail-qc0-f182.google.com with SMTP id k19so1353516qcs.27 for ; Mon, 25 Feb 2013 06:19:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-received:content-type:mime-version:subject:from:in-reply-to:date :content-transfer-encoding:message-id:references:to:x-mailer :x-gm-message-state; bh=AwWHNkUxyBqPQNqZ0vO/v3dJQzwPFK3V4lr4/CPCB3M=; b=nOzyrhtLilC3gSVvnPR6C8K+OcXoY7oEbJ8obpNEzXfvq2i7VC+P6A24N1vDlzin3T rEH70dMSWi5ooSSqgCswnOf/o7lL0bH+A55PRh4pYgCFBamWS2MOqP2ZteQmJbP+I5lL FK8phsluQedPnqnYRXS4A8zXiF+l5JCdwHHh5TuJffnNLygIjxivHxuYlYPpNskrdnQX 07T3Vxp8yLspGpLDCbp/D7+wDSfdSo1TJ9hmCUesBprbp94NgQJVQKLw6JH56vtR2tqU uA2RLoLPVxBvI0n7AbfFB01efQy1Cg7FcYReIDt/hXeIANjcQgCdXIc8Jbts8aESaLaH HWlA== X-Received: by 10.224.199.70 with SMTP id er6mr11478675qab.19.1361801966433; Mon, 25 Feb 2013 06:19:26 -0800 (PST) Received: from [192.168.2.99] ([96.236.21.119]) by mx.google.com with ESMTPS id hr3sm16679870qab.4.2013.02.25.06.19.25 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 25 Feb 2013 06:19:26 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: Strange delays in ZFS scrub or resilver From: Paul Kraus In-Reply-To: <20130224042340.11192.qmail@joyce.lan> Date: Mon, 25 Feb 2013 09:19:28 -0500 Content-Transfer-Encoding: quoted-printable Message-Id: <7BEF43DD-9920-4923-BF21-A16CDD570F4C@kraus-haus.org> References: <20130224042340.11192.qmail@joyce.lan> To: "freebsd-questions@freebsd.org List" X-Mailer: Apple Mail (2.1499) X-Gm-Message-State: ALoCoQnuPVVYbD79ZX4SZ1d1oKM35SpQf9Ap6B5altC00DSTZYf/ETq5VY8SIGRSded4F1WdLBmu X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 25 Feb 2013 14:19:33 -0000 On Feb 23, 2013, at 11:23 PM, John Levine wrote: > I have a raidz of three 1 TB SATA drives, in USB enclosures. One of > the disks went bad, so I replaced it last night and it's been > resilvering ever since. I can watch the activity lights on the disks > and it cranks away for a minute or so, then stops for a minute, then > cranks for a minute, and so forth. If I do a zpool status while it's > stopped, the zpool waits until the I/O resumes, and a ^T shows it > waiting for zio->io_cv. >=20 > I'm running FreeBSD 9.1, amd64 version, totally vanilla install on a > mini-itx box with 4GB of RAM. The root/swap disk is an SSD separate > from the zfs disks. When the disks are active, top shows about 10% > system time and 4% interrupt. When it isn't, top shows about 99.8% > idle. The server isn't doing much else, and nothing else currently > touches the disks. (They're for remote backup of a system somewhere > else, and I have the backup job turned off until resilvering > completes.) Under 9.0 I had some external drives attached via USB and saw = truly terrible I/O performance. I moved them to ESATA and it got much = better. Unfortunately, my external exclosure has a SATA port expander as = I need to talk to 4 external drives. That gives me about a factor of 2 = worse performance than the internal SATA drives (even if I am only = talking to one drive via the external connection). -- Paul Kraus Deputy Technical Director, LoneStarCon 3 Sound Coordinator, Schenectady Light Opera Company