From owner-freebsd-stable@FreeBSD.ORG Fri Jan 7 12:59:34 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2B8341065674 for ; Fri, 7 Jan 2011 12:59:34 +0000 (UTC) (envelope-from ml@my.gd) Received: from mail-ww0-f42.google.com (mail-ww0-f42.google.com [74.125.82.42]) by mx1.freebsd.org (Postfix) with ESMTP id B61DB8FC0C for ; Fri, 7 Jan 2011 12:59:33 +0000 (UTC) Received: by wwi17 with SMTP id 17so427138wwi.1 for ; Fri, 07 Jan 2011 04:59:32 -0800 (PST) Received: by 10.227.155.15 with SMTP id q15mr15488272wbw.64.1294405172618; Fri, 07 Jan 2011 04:59:32 -0800 (PST) Received: from dfleuriot.local ([83.167.62.196]) by mx.google.com with ESMTPS id 11sm17643850wbj.19.2011.01.07.04.59.31 (version=SSLv3 cipher=RC4-MD5); Fri, 07 Jan 2011 04:59:31 -0800 (PST) Message-ID: <4D270E32.30801@my.gd> Date: Fri, 07 Jan 2011 13:59:30 +0100 From: Damien Fleuriot User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7 MIME-Version: 1.0 To: freebsd-stable@freebsd.org References: <4D1C6F90.3080206@my.gd> <4D21E679.80002@my.gd> <84882169-0461-480F-8B4C-58E794BCC8E6@my.gd> <488AE93A-97B9-4F01-AD0A-0098E4B329C3@my.gd> <20110107014249.GA3719@icarus.home.lan> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 07 Jan 2011 12:59:34 -0000 On 1/7/11 1:10 PM, Markiyan Kushnir wrote: > 2011/1/7 Jeremy Chadwick : >> On Fri, Jan 07, 2011 at 12:29:17PM +1100, Jean-Yves Avenard wrote: >>> On 6 January 2011 22:26, Chris Forgeron wrote: >>>> You know, these days I'm not as happy with SSD's for ZIL. I may blog about some of the speed results I've been getting over the last 6mo-1yr that I've been running them with ZFS. I think people should be using hardware RAM drives. You can get old Gigabyte i-RAM drives with 4 gig of memory for the cost of a 60 gig SSD, and it will trounce the SSD for speed. >>>> >>>> I'd put your SSD to L2ARC (cache). >>> >>> Where do you find those though. >>> >>> I've looked and looked and all references I could find was that >>> battery-powered RAM card that Sun used in their test setup, but it's >>> not publicly available.. >> >> DDRdrive: >> http://www.ddrdrive.com/ >> http://www.engadget.com/2009/05/05/ddrdrives-ram-based-ssd-is-snappy-costly/ >> >> ACard ANS-9010: >> http://techreport.com/articles.x/16255 >> >> GC-RAMDISK (i-RAM) products: >> http://us.test.giga-byte.com/Products/Storage/Default.aspx >> >> Be aware these products are absurdly expensive for what they offer (the >> cost isn't justified), not to mention in some cases a bottleneck is >> imposed by use of a SATA-150 interface. I'm also not sure if all of >> them offer BBU capability. >> >> In some respects you might be better off just buying more RAM for your >> system and making md(4) memory disks that are used by L2ARC (cache). >> I've mentioned this in the past (specifically "back in the days" when >> the ARC piece of ZFS on FreeBSD was causing havok, and asked if one >> could work around the complexity by using L2ARC with md(4) drives >> instead). >> > > Once you have got extra RAM, why not just reserve it directly to ARC > (via vm.kmem_size[_max] and vfs.zfs.arc_max)? > > Markiyan. > I haven't calculated yet but perhaps SSDs are cheaper by the GB than raw RAM. Not to mention DIMM slots are usually scarce, disk ones aren't.