From owner-freebsd-questions@FreeBSD.ORG Sat Apr 7 00:18:22 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 0794416A409 for ; Sat, 7 Apr 2007 00:18:22 +0000 (UTC) (envelope-from mike@nux.co.uk) Received: from smtp.nildram.co.uk (smtp.nildram.co.uk [195.112.4.54]) by mx1.freebsd.org (Postfix) with ESMTP id C5B0213C4B0 for ; Sat, 7 Apr 2007 00:18:21 +0000 (UTC) (envelope-from mike@nux.co.uk) Received: from office.nux.co.uk (unknown [82.133.40.67]) by smtp.nildram.co.uk (Postfix) with ESMTP id 3B2BB2B8250 for ; Sat, 7 Apr 2007 00:48:51 +0100 (BST) Received: (qmail 93826 invoked by uid 2223); 6 Apr 2007 23:48:51 -0000 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 6 Apr 2007 23:48:51 -0000 Date: Sat, 7 Apr 2007 00:48:51 +0100 (BST) From: Mike Wolman X-X-Sender: mike@nux.eros.office To: freebsd-fs@FreeBSD.org, freebsd-questions@freebsd.org In-Reply-To: <20070406214804.GC61039@garage.freebsd.pl> Message-ID: <20070407001555.G87655@nux.eros.office> References: <20070406025700.GB98545@garage.freebsd.pl> <4615F62A.5090001@FreeBSD.org> <20070406214804.GC61039@garage.freebsd.pl> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: Subject: some thoughts about gmirror 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: Sat, 07 Apr 2007 00:18:22 -0000 Hi, Currently I am using gmirror and ggated to run a live network mirror. Obviously this can cause problems if the server exporting the 'backup' device is offline then the mirror is broken - when the machines reconnect a full mirror sync takes place. This is fine over gbit crossover and if the size of the mirror is only a few 100Gb. Is it feasible that when the connection to one of the mirror devices breaks gmirror starts to log the changes to the mirror (obviously you would need to configure up this mirror device as a 'lazy' mirror member with a spare local device to write the changes to) - when the machines reconnect gmirror would only then have to sync the actual changes. This is sort of achieves a similar result to Live Network Backup on NetBSD (http://kerneltrap.org/node/5058). It could be used for laptop users mirroring their whole drive, allowing a fast sync when they are on their local lan and should the laptop get lost it would be possible to restore the whole machine with a simple dd. If they were using a usb key as the device to log the changes while they were disconnected from the network and they remember to unplug/plug this each time they use the laptop then it could even be possible to recover the data to the point they actually lost the machine. It could also be used for asynchronous mirrors over slow links, if the log device was always written to first then the write latency for long distant links could be removed. Im not sure if it would be possible to achieve this using just a modified ggatec instead which has a local device used as a write cache. Mike.