From owner-freebsd-fs@FreeBSD.ORG Mon Apr 9 23:09:29 2007 Return-Path: X-Original-To: freebsd-fs@freebsd.org Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 5CCC616A401 for ; Mon, 9 Apr 2007 23:09:29 +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 222FD13C448 for ; Mon, 9 Apr 2007 23:09:29 +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 BC8662B74D3 for ; Tue, 10 Apr 2007 00:09:27 +0100 (BST) Received: (qmail 45158 invoked by uid 2223); 9 Apr 2007 23:09:27 -0000 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 9 Apr 2007 23:09:27 -0000 Date: Tue, 10 Apr 2007 00:09:27 +0100 (BST) From: Mike Wolman X-X-Sender: mike@nux.eros.office To: Eric Anderson In-Reply-To: <461A4CCC.8060205@freebsd.org> Message-ID: <20070409235056.R44017@nux.eros.office> References: <20070406025700.GB98545@garage.freebsd.pl> <4615F62A.5090001@FreeBSD.org> <20070406214804.GC61039@garage.freebsd.pl> <20070407001555.G87655@nux.eros.office> <461A4CCC.8060205@freebsd.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-fs@freebsd.org Subject: Re: some thoughts about gmirror X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Apr 2007 23:09:29 -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. > > > Personally, I think this would be a very useful feature. This is sort of > like snapshots for GEOM, which would be useful in other ways too. GEOM > journaling, GEOM snapshots, and this lazy mirroring are all somewhat similar > it seems. > > Are you proposing to write such a feature? Even if you can't code it, > writing up the design/specs might help someone actually implement it. > > > Eric > My initial thoughts were for fast recovery from a non failed mirror device but realised it could be used for many other things from mobile users to remote asyncs. I had not thought of using it for snapshots but i can see where your coming from - by simply keeping the changes you could rewind to any point in time without having to actually create a snapshot(s) beforehand. I only wish my os/file system/geom knowledge was up to even specifying this, let alone my complete lack of c programming ability. However I can try to put together a specification from a system admins perspective if that is of any help? And of course i would be more than willing to test test test. Mike.