From owner-freebsd-questions@FreeBSD.ORG Sun Feb 21 07:50:28 2010 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id BB2F7106566B for ; Sun, 21 Feb 2010 07:50:28 +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 67F1E8FC16 for ; Sun, 21 Feb 2010 07:50:28 +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 o1L7oRt8002550 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Sun, 21 Feb 2010 01:50:27 -0600 (CST) (envelope-from dan@dan.emsphone.com) Received: from dan.emsphone.com (smmsp@localhost [127.0.0.1]) by dan.emsphone.com (8.14.4/8.14.3) with ESMTP id o1L7oRJj050907 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Sun, 21 Feb 2010 01:50:27 -0600 (CST) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.14.4/8.14.3/Submit) id o1L7oRcD050887; Sun, 21 Feb 2010 01:50:27 -0600 (CST) (envelope-from dan) Date: Sun, 21 Feb 2010 01:50:26 -0600 From: Dan Nelson To: Aiza Message-ID: <20100221075026.GL70798@dan.emsphone.com> References: <4B80ABBA.9000707@comclark.com> <20100221061449.GK70798@dan.emsphone.com> <4B80E4AF.3040204@comclark.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4B80E4AF.3040204@comclark.com> X-OS: FreeBSD 7.2-STABLE User-Agent: Mutt/1.5.20 (2009-06-14) X-Virus-Scanned: clamav-milter 0.95.3 at 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]); Sun, 21 Feb 2010 01:50:27 -0600 (CST) X-Scanned-By: MIMEDefang 2.45 Cc: freebsd-questions Subject: Re: Dump questions 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: Sun, 21 Feb 2010 07:50:28 -0000 In the last episode (Feb 21), Aiza said: > Dan Nelson wrote: > > In the last episode (Feb 21), Aiza said: > >> 1. Using the -L flag to create a snapshot of the live running file > >> system. > >> > >> Does this mean that a complete copy of the file system is written to > >> .snap directory? > > > > No; that would be a "copy". Snapshots only copy blocks as they are > > modified on the parent filesystem, so their size is determined by how > > much data is modified since the snapshot was created. > > So how does this interact with the dump process? > > Dump start reading and writing its dump file and as the live system > changes the changes are written to the .snap and when dump completes it > overwrites it dump with the changes from the .snap??? > > How does this process work in detail? Dump reads from the snapshot, which is guaranteed not to change while dump is running. When its done, dump deletes the snapshot file. Changes made after the dump has started will not be saved. This is the same as any other backup system that uses snapshots afaik; none try and catch up changes made while the backup itself is running. You could run another incremental dump right after the previous one, which would back up any changes since the first one. -- Dan Nelson dnelson@allantgroup.com