From owner-freebsd-questions@FreeBSD.ORG Fri Jun 1 15:35:32 2012 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3BD3D106567D for ; Fri, 1 Jun 2012 15:35:32 +0000 (UTC) (envelope-from dan@dan.emsphone.com) Received: from email2.allantgroup.com (firebox.emsphone.com [199.67.51.15]) by mx1.freebsd.org (Postfix) with ESMTP id CEC828FC0C for ; Fri, 1 Jun 2012 15:35:31 +0000 (UTC) Received: from dan.emsphone.com (dan.emsphone.com [172.17.17.101]) by email2.allantgroup.com (8.14.4/8.14.4) with ESMTP id q51FZPFg058067 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 1 Jun 2012 10:35:26 -0500 (CDT) (envelope-from dan@dan.emsphone.com) Received: from dan.emsphone.com (smmsp@localhost [127.0.0.1]) by dan.emsphone.com (8.14.5/8.14.5) with ESMTP id q51FZPYe064062 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 1 Jun 2012 10:35:25 -0500 (CDT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.14.5/8.14.5/Submit) id q51FZPXJ064061; Fri, 1 Jun 2012 10:35:25 -0500 (CDT) (envelope-from dan) Date: Fri, 1 Jun 2012 10:35:25 -0500 From: Dan Nelson To: Wojciech Puchar Message-ID: <20120601153525.GA16874@dan.emsphone.com> References: <20120601163520.f130cdcd.freebsd@edvax.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-OS: FreeBSD 8.3-PRERELEASE User-Agent: Mutt/1.5.21 (2010-09-15) X-Virus-Scanned: clamav-milter 0.97.2 at email2.allantgroup.com X-Virus-Status: Clean X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.6 (email2.allantgroup.com [172.17.19.78]); Fri, 01 Jun 2012 10:35:26 -0500 (CDT) X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,T_RP_MATCHES_RCVD autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on email2.allantgroup.com X-Scanned-By: MIMEDefang 2.68 on 172.17.19.78 Cc: Kaya Saman , Polytropon , freebsd-questions@freebsd.org Subject: Re: Anyone using freebsd ZFS for large storage servers? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Jun 2012 15:35:32 -0000 In the last episode (Jun 01), Wojciech Puchar said: > > and unbelievable narrow cases, when you don't have or can't access a > > backup (which you should have even when using ZFS), and you _need_ to do > > some forensic analysis on disks, ZFS seems to be a worse solution than > > UFS. On ZFS, you never can predict where the data will go. Add several > > disks to > > true. in UFS for example inodes are at known place, and flat structure > instead of "tree" is used. > > even if some sectors are overwritten with garbage then fsck can scan over > inodes and recover all that can be recovered. > > ZFS is somehow in that part similar to Amiga "Fast" File System. when you > overwrite a directory block (by hardware fault for example), everything > below that directory will disappear. You may not be even aware of it > until you need that data On the other hand, even on a single-disk pool, ZFS stores two copies of all metadata, so the chances of actually losing a directory block are extremely remote. On mirrored or RAIDZ pools, you have at least four copies of all metadata. -- Dan Nelson dnelson@allantgroup.com