From owner-freebsd-stable@FreeBSD.ORG Tue Mar 5 03:25:19 2013 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 9E8DFE16 for ; Tue, 5 Mar 2013 03:25:19 +0000 (UTC) (envelope-from prvs=1776ac14af=killing@multiplay.co.uk) Received: from mail1.multiplay.co.uk (mail1.multiplay.co.uk [85.236.96.23]) by mx1.freebsd.org (Postfix) with ESMTP id 20FECBE8 for ; Tue, 5 Mar 2013 03:25:18 +0000 (UTC) Received: from r2d2 ([46.65.172.4]) by mail1.multiplay.co.uk (mail1.multiplay.co.uk [85.236.96.23]) (MDaemon PRO v10.0.4) with ESMTP id md50002544721.msg for ; Tue, 05 Mar 2013 03:25:16 +0000 X-Spam-Processed: mail1.multiplay.co.uk, Tue, 05 Mar 2013 03:25:16 +0000 (not processed: message from valid local sender) X-MDDKIM-Result: neutral (mail1.multiplay.co.uk) X-MDRemoteIP: 46.65.172.4 X-Return-Path: prvs=1776ac14af=killing@multiplay.co.uk X-Envelope-From: killing@multiplay.co.uk X-MDaemon-Deliver-To: freebsd-stable@freebsd.org Message-ID: <8C68812328E3483BA9786EF15591124D@multiplay.co.uk> From: "Steven Hartland" To: "Karl Denninger" , References: <513524B2.6020600@denninger.net> <1362449266.92708.8.camel@btw.pki2.com> <51355F64.4040409@denninger.net> Subject: Re: ZFS "stalls" -- and maybe we should be talking about defaults? Date: Tue, 5 Mar 2013 03:25:18 -0000 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 05 Mar 2013 03:25:19 -0000 ----- Original Message ----- From: "Karl Denninger" > Stick this in /boot/loader.conf and see if your lockups goes away: > > vfs.zfs.write_limit_override=1024000000 ... > If it turns out that the write_limit_override tunable is the one > responsible for stopping the hangs I can drop the ARC limit tunable > although I'm not sure I want to; I don't see much if any performance > penalty from leaving it where it is and if the larger cache isn't > helping anything then why use it? I'm inclined to stick an SSD in the > cabinet as a cache drive instead of dedicating RAM to this -- even > though it's not AS fast as RAM it's still MASSIVELY quicker than getting > data off a rotating plate of rust. Now interesting you should say that I've seen a stall recently on ZFS only box running on 6 x SSD RAIDZ2. The stall was caused by fairly large mysql import, with nothing else running. Then it happened I thought the machine had wedged, but minutes (not seconds) later, everything sprung into action again. > Am I correct that a ZFS filesystem does NOT use the VM buffer cache > at all? Correct Regards Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 or return the E.mail to postmaster@multiplay.co.uk.