From owner-freebsd-current@FreeBSD.ORG Wed Nov 11 20:49:05 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 50912106568B for ; Wed, 11 Nov 2009 20:49:05 +0000 (UTC) (envelope-from dan@dan.emsphone.com) Received: from email1.allantgroup.com (email1.emsphone.com [199.67.51.115]) by mx1.freebsd.org (Postfix) with ESMTP id 160B38FC16 for ; Wed, 11 Nov 2009 20:49:04 +0000 (UTC) Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by email1.allantgroup.com (8.14.0/8.14.0) with ESMTP id nABKn4Gp089817 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 11 Nov 2009 14:49:04 -0600 (CST) (envelope-from dan@dan.emsphone.com) Received: from dan.emsphone.com (smmsp@localhost [127.0.0.1]) by dan.emsphone.com (8.14.3/8.14.3) with ESMTP id nABKn4xD080348 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 11 Nov 2009 14:49:04 -0600 (CST) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.14.3/8.14.3/Submit) id nABKn3ln080333; Wed, 11 Nov 2009 14:49:03 -0600 (CST) (envelope-from dan) Date: Wed, 11 Nov 2009 14:49:03 -0600 From: Dan Nelson To: Ivan Voras Message-ID: <20091111204903.GI89052@dan.emsphone.com> References: <11167f520911111050j36dd94far667c81e6f5c18e69@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-OS: FreeBSD 7.2-STABLE User-Agent: Mutt/1.5.20 (2009-06-14) X-Virus-Scanned: ClamAV version 0.94.1, clamav-milter version 0.94.1 on email1.allantgroup.com X-Virus-Status: Clean X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0.2 (email1.allantgroup.com [199.67.51.78]); Wed, 11 Nov 2009 14:49:04 -0600 (CST) X-Scanned-By: MIMEDefang 2.45 Cc: freebsd-current@freebsd.org Subject: Re: Help ZFS FreeBSD 8.0 RC2 Write performance issue X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 Nov 2009 20:49:05 -0000 In the last episode (Nov 11), Ivan Voras said: > Sam Fourman Jr. wrote: > > I am running FreeBSD 8.0RC2 and I dont understand why my ZFS/NFS is > > acting weird on writes. I get ~150mbit writes idk if this is good or > > not? but it paused for a few seconds every once and awhile. > > You didn't give any "iostat" statistics - I suspect that if you > correlate ifstat and iostat output that you will see that network > "pauses" happen during spikes in IO. You should check for this and post > your results. Yes, iostat would be useful here. "iostat -zxC 2" will give you per-disk stats plus CPU usage every 2 seconds (CPU may be a factor if you have compression enabled). On a Solaris box I admin, setting zfs_write_limit_override helped stuttering while doing heavy writes. It's not exported on FreeBSD, but it should be easy to add it as a RW sysctl; it lives in dsl_pool.c and can be tweaked at runtime. Start big and tune it down so each write burst takes under a second; it looks like you're writing solid for around 6-8 seconds now. The number will vary depending on your disk speed and how much ARC you have. -- Dan Nelson dnelson@allantgroup.com