Date: Tue, 10 Apr 2007 00:09:27 +0100 (BST) From: Mike Wolman <mike@nux.co.uk> To: Eric Anderson <anderson@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: some thoughts about gmirror Message-ID: <20070409235056.R44017@nux.eros.office> In-Reply-To: <461A4CCC.8060205@freebsd.org> References: <20070406025700.GB98545@garage.freebsd.pl> <4615F62A.5090001@FreeBSD.org> <20070406214804.GC61039@garage.freebsd.pl> <20070407001555.G87655@nux.eros.office> <461A4CCC.8060205@freebsd.org>
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>> 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.
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