From owner-freebsd-scsi@freebsd.org Tue Oct 3 07:39:37 2017 Return-Path: Delivered-To: freebsd-scsi@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 C1166E338CC for ; Tue, 3 Oct 2017 07:39:37 +0000 (UTC) (envelope-from steven@multiplay.co.uk) Received: from mail-wm0-x22d.google.com (mail-wm0-x22d.google.com [IPv6:2a00:1450:400c:c09::22d]) (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 4FAE568825 for ; Tue, 3 Oct 2017 07:39:37 +0000 (UTC) (envelope-from steven@multiplay.co.uk) Received: by mail-wm0-x22d.google.com with SMTP id t69so14725429wmt.2 for ; Tue, 03 Oct 2017 00:39:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=multiplay-co-uk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language; bh=GrdDugNggHtWHMaNQfG4aSNyt9oH2g9RwDNn/ftgLmU=; b=zZz6wklD5H1NP7KE7l9LGGs5UxEBQlB10BWB9S7z2eQ6hO+aVWxEkMMwa+GtjshS8Y Cxz80LYM10mwFk952Xdu5MXzeUnKBQyYUvvZRHCicz/TCheQXglNww/jqWLBHLmneqiL nK4IclmVMoCZgEh8vvnhMr6iydaXuC0jtJoUCre5tLZIbXJAsVeNQBPAVTbMOlamk4ll BJ76b4zy8WeP7FPmEZPjGt2xuJnkWYsxC1bJ2JuqfXs3rJQvVHEB4wIw1CUNnvZo9HtW Lh1uqp2wd0HtrHu5GSW/sigE/wqu/nBtaeQdpjGYcCsLl1+PE2mOBTrqdRRT8XlbtifE dhtA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language; bh=GrdDugNggHtWHMaNQfG4aSNyt9oH2g9RwDNn/ftgLmU=; b=YRvLA22tLfXeMUIXiWk9x7DevUUJgPEz9U9oW56t+sqS4c2P+PyAGzCQRDS/QCLQCp dDGexNYP9p+NvNxAXCNFRKavGbX81/7KTQ7L7KiRrLv9RzaH0rFWt/87Wttuo3CKMMez kHzwGj28GF94DfyUGr9pqcjoi5AC3ekCUIWvlu7FG9if7pCgftC9gGiIwNgHEb5007FV iX8dK7BUD0QurQL9a6cuBGvrz/AXjP7abli3EyTJsYIxJMFrnHyU3D5kr3+1fik6S5kT i70iidsiATE+wm3ZHZmzeqblVbYr+oE7m1sBGhIg6ufJ4V00wrY7M+2t+PQBK2mEnSgO hNLQ== X-Gm-Message-State: AHPjjUg0jvc3ClLoTrN/YZFWIfjiZpyJjouB7BELpujOBT1m3AWdkaa9 xim+bTGBq4/T986gmEn3pBo6QP9fE54= X-Google-Smtp-Source: AOwi7QABtvOBGfjQMvW7El+S9dNwANMh3rBpWLRCo55zipq8qtcFGcIWNwwI7ug+klEOpwEH9VtYSg== X-Received: by 10.80.183.231 with SMTP id i36mr22667458ede.262.1507016375361; Tue, 03 Oct 2017 00:39:35 -0700 (PDT) Received: from [10.10.1.111] ([185.97.61.1]) by smtp.gmail.com with ESMTPSA id f20sm9116958edm.46.2017.10.03.00.39.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 03 Oct 2017 00:39:34 -0700 (PDT) Subject: Re: ZFS stalled after some mirror disks were lost To: Ben RUBSON , Andriy Gapon Cc: Freebsd fs , FreeBSD-scsi References: <4A0E9EB8-57EA-4E76-9D7E-3E344B2037D2@gmail.com> <69fbca90-9a18-ad5d-a2f7-ad527d79f8ba@freebsd.org> <1990B359-FC8D-4D6A-992B-7F77A07D83A6@gmail.com> From: Steven Hartland Message-ID: <9bce89eb-4d6f-aec1-df44-ebf794a3123b@multiplay.co.uk> Date: Tue, 3 Oct 2017 08:39:36 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <1990B359-FC8D-4D6A-992B-7F77A07D83A6@gmail.com> Content-Language: en-US Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Content-Filtered-By: Mailman/MimeDel 2.1.23 X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 Oct 2017 07:39:37 -0000 On 03/10/2017 08:31, Ben RUBSON wrote: >> On 03 Oct 2017, at 09:25, Steven Hartland wrote: >> >> On 03/10/2017 07:12, Andriy Gapon wrote: >>> On 02/10/2017 21:12, Ben RUBSON wrote: >>> >>>> A sustained read throughput of 180 MB/s, 45 MB/s on each iscsi disk >>>> according to "zpool iostat", nothing on local disks (strange but I >>>> noticed that IOs always prefer iscsi disks to local disks). >>>> >>> Are your local disks SSD or HDD? >>> Could it be that iSCSI disks appear to be faster than the local disks to the >>> smart ZFS mirror code? >>> >>> Steve, what do you think? >>> >> Yes that quite possible, the mirror balancing uses the queue depth + rotating bias to determine the load of the disk so if your iSCSI host is processing well and / or is reporting non-rotating vs rotating for the local disks it could well be the mirror is preferring reads from the the less loaded iSCSI devices. > Note that local & iscsi disks are _exactly_ the same (same model number, same SAS adapter...). > So iSCSI ones should be a little bit slower due to network latency (even if it's very low in my case). > Once production back, after having analysed the main issue of this thread, I should then > try to find whether or not iSCSI disks are seen as rotating disks. > > Thanks for the hint ! Hmm, the output from gstat -dp on a loaded machine would be interesting to see too.     Regards     Steve