Date: Wed, 31 Mar 2010 10:22:43 +0100 From: Mike Clarke <jmc-freebsd2@milibyte.co.uk> To: freebsd-questions@freebsd.org Subject: Re: Copying mirrored partitions - will this work? Message-ID: <201003311022.44297.jmc-freebsd2@milibyte.co.uk> In-Reply-To: <201003201532.48793.jmc-freebsd2@milibyte.co.uk> References: <201003201532.48793.jmc-freebsd2@milibyte.co.uk>
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On Saturday 20 March 2010, Mike Clarke wrote: > I'm currently running 8.0-RELEASE and am considering experimenting > with 8.0-STABLE. I'd like to preserve my existing system in case > things go pear-shaped so I'll copy the entire system onto a spare > slice and then use csup to upgrade the copy to STABLE. Normally I'd > go through the steps of bsdlabel, newfs and then dump|restore to > create the copy but I'm wondering if I can take advantage of my > recently created gmirror to cut down the work. > > I have two 500GB disks, /dev/ad4 and /dev/ad8, each partitioned into > 4 slices of 88, 88, 42 and 259GB. My system is installed on the first > slices (ad4s1 and ad8s1) which are mirrored as /dev/mirror/gm0. The > second slices (ad4s2 and ad8s2) are currently unused. My thoughts are > to temporarily add ad4s2 into gm0 with "gmirror insert gm0 ad4s2" and > wait for the mirror to synchronise. I should then be able to remove > the temporary addition with "gmirror remove gm0 /dev/ad4s2" at which > point ad4s2 should be a duplicate of the original system and I can > then go ahead and create a new mirror with "gmirror label -b load gm1 > ad4s2" and "gmirror insert gm1 ad8s2". After editing /etc/fstab in > the new mirror to use gm1 instead of gm0 I should then be able to > boot into the system on slice 2 and upgrade it to STABLE while still > keeping my original system to fall back to if required. > > Is this approach of moving disks from one mirror to another workable, > or have I missed something that would lead me into deep trouble? I > don't mind unduly if I make a mess of the second slice and have to > start again but I don't want to lose the contents of my original > system on slice 1. I decided to give it a try and the process went through very smoothly. It was much less tedious than bsdlabel -> newfs -> dump|restore, and quicker too. The mirror synchronised at a bit over 100 MB/sec but dump| restore only gave me about 10 MB/sec. The system has now been running for a bit over a week without any problems with either the original or cloned slices so I'm quite confident that things are OK. -- Mike Clarke
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