From owner-freebsd-fs@FreeBSD.ORG Wed May 11 09:48:47 2011 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 5B301106564A for ; Wed, 11 May 2011 09:48:47 +0000 (UTC) (envelope-from fbsd@dannysplace.net) Received: from mailgw.dannysplace.net (mailgw.dannysplace.net [204.109.56.184]) by mx1.freebsd.org (Postfix) with ESMTP id E1E8F8FC15 for ; Wed, 11 May 2011 09:48:46 +0000 (UTC) Received: from [203.206.171.212] (helo=[192.168.10.10]) by mailgw.dannysplace.net with esmtpsa (TLSv1:CAMELLIA256-SHA:256) (Exim 4.72 (FreeBSD)) (envelope-from ) id 1QK5ju-0006WU-78 for freebsd-fs@freebsd.org; Wed, 11 May 2011 19:29:55 +1000 Message-ID: <4DCA5620.1030203@dannysplace.net> Date: Wed, 11 May 2011 19:25:52 +1000 From: Danny Carroll User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.2.17) Gecko/20110414 Lightning/1.0b2 Thunderbird/3.1.10 MIME-Version: 1.0 To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Authenticated-User: danny X-Authenticator: plain X-Exim-Version: 4.72 (build at 12-Jul-2010 18:31:29) X-Date: 2011-05-11 19:29:54 X-Connected-IP: 203.206.171.212:58231 X-Message-Linecount: 35 X-Body-Linecount: 24 X-Message-Size: 1393 X-Body-Size: 944 X-Received-Count: 1 X-Recipient-Count: 1 X-Local-Recipient-Count: 1 X-Local-Recipient-Defer-Count: 0 X-Local-Recipient-Fail-Count: 0 X-SA-Exim-Connect-IP: 203.206.171.212 X-SA-Exim-Mail-From: fbsd@dannysplace.net X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on damka.dannysplace.net X-Spam-Level: X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.3.1 X-SA-Exim-Version: 4.2 X-SA-Exim-Scanned: Yes (on mailgw.dannysplace.net) Subject: ZFS: How to enable cache and logs. X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: fbsd@dannysplace.net List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 May 2011 09:48:47 -0000 Hello all. I've been using ZFS for some time now and have never had an issued (except perhaps the issue of speed...) When v28 is taken into -STABLE I will most likely upgrade to v28 at that point. Currently I am running v15 with v4 on disk. When I move to v28 I will probably wish to enable a L2Arc and also perhaps dedicated log devices. I'm curious about a few things however. 1. Can I remove either the L2 ARC or the log devices if things don't go as planned or if I need to free up some resources? 2. What are the best practices for setting up these? Would a geom mirror for the log device be the way to go. Or can you just let ZFS mirror the log itself? 3. What happens when one or both of the log devices fail. Does ZFS come to a crashing halt and kill all the data? Or does it simply complain that the ZIL is no longer active and continue on it's merry way? In short, what is the best way to set up these two features? -D