From owner-freebsd-fs@FreeBSD.ORG Fri Oct 31 09:21:00 2008 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id DF485106567C for ; Fri, 31 Oct 2008 09:21:00 +0000 (UTC) (envelope-from numisemis@yahoo.com) Received: from web36603.mail.mud.yahoo.com (web36603.mail.mud.yahoo.com [209.191.85.20]) by mx1.freebsd.org (Postfix) with SMTP id 90B468FC1C for ; Fri, 31 Oct 2008 09:21:00 +0000 (UTC) (envelope-from numisemis@yahoo.com) Received: (qmail 18399 invoked by uid 60001); 31 Oct 2008 09:20:59 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:Date:From:Reply-To:Subject:To:MIME-Version:Content-Type:Message-ID; b=f0Qkp8pUGu9d1eONa4VW/Zhc7gRmbXGt8jwqT1u8do1nUAmzcKYzok4y5UdzheyNJjRpx1LYkA7Q/mP73mNUKyHLDCQOeRpedosg1P5DQLzwd1uy8SMtpmH7uV3vuOANgwEbHkppIDEqPSGBTIcMiwJoMh0o4p6xJi0p0iYrf6w=; X-YMail-OSG: tE_zPJYVM1nwdJxd.8xh3pfo1Y1WdeEAD4qBiLlqPqNSOlaQlYMdXeuhrZG9W3lgyvZ.xhXBfwtXXSSDqDisLdzLhCPzRcXMT51uqy6uhguBADCyQ9BIkAwLiDys3VbYSI_a Received: from [213.147.110.159] by web36603.mail.mud.yahoo.com via HTTP; Fri, 31 Oct 2008 02:20:59 PDT X-Mailer: YahooMailWebService/0.7.260.1 Date: Fri, 31 Oct 2008 02:20:59 -0700 (PDT) From: Simun Mikecin To: freebsd-fs@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Message-ID: <880498.17704.qm@web36603.mail.mud.yahoo.com> X-Mailman-Approved-At: Fri, 31 Oct 2008 11:23:36 +0000 Subject: Re: Areca vs. ZFS performance testing. X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: numisemis@yahoo.com List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 31 Oct 2008 09:21:01 -0000 Jeremy Chadwick wrote: > The tuning variables I advocate for a system with 2GB of RAM or more, > on RELENG_7, are: > vm.kmem_size="1536M" > vm.kmem_size_max="1536M" There is no point in setting vm.kmem_size_max. Setting vm.kmem_size is enough. vm.kmem_size_max is used for auto-tuning of kmem size which is in this case actually overriden by manually setting vm.kmem_size. > vfs.zfs.arc_min="16M" > vfs.zfs.arc_max="64M" > vfs.zfs.prefetch_disable="1" > You can gradually increase arc_min and arc_max by > ~16MB increments as > you see fit; you should see general performance > improvements as they > get larger (more data being kept in the ARC), but > don't get too crazy. > I've tuned arc_max up to 128MB before with > success, but I don't want > to try anything larger without decreasing kmem_size_*. Can you explain why would you have to decrease kmem_size to use larger ARC? AFAIK it should be contrary to what you are saying: when you use larger kmem_size you can also use larger arc_max. My suggestion if you are using kmem_size of 1536M would be to not tune arc_min and arc_max if your system isn't panicing. If it does you should try decreasing arc_max (from it's default value) until it doesn't.