Rick, You're laughing. Having a completely unused disk available makes the job _so_ much easier.
On Thu, Feb 16, 2006 at 01:26:31PM -0500, Rick DeNatale wrote: > Having just recovered from a failed SCSI hard drive, I'd now like to > put my second SCSI drive to work mirroring the first. > > I've always had good backups of my user and config data, but it was > still a pain to get my machine back on it's feet. > > When I replaced the drive, I re-installed Ubuntu 5.10 on /dev/sda using LVM. > > The installer setup two partitions, one for /boot and another for an > LVM PV, and one VG with two LVs, one for /root and one for swap. > > I'd now like to jack that up and install MDM software raid under it. > The Ubuntu kernel seems to be built with support for mdadm raid. I've > looked at a few how-tos but my head is still swimming and I'm, as > always leery of doing low-level drive operations. I've also backed up > /dev/sda using g4linux. Belt _and_ suspenders, I like that. > It looks like the trick is to duplicate the partitioning of /dev/sda > on /dev/sdb after changing partition types to Linux raid autodetect, actually, before. On sdb you create a partition that is the same size as your sda LVM partition, and then use the rest for, say, swap or temp. > and then do some mdmadmin magic to create a raid "device". I'm a Correct. I'm sure that others will also observe that there are a couple of approaches. One would be: Make sdb2 of type raid autodetect, and then configure mdadm to see it as a RAID 1, half-partition. ( "broken", in that there is no actual mirror drive, yet. ) Since md presents the view of a "disk drive" to all layers above, including LVM, LVM won't know or care what kind of "disk drive" it is running on. Create a new PV using the new md partition, and allocate a new VG on that PV. Create a new LV on that VG, of appropriate size, format it and copy all of / on to that new LV. Swap sdb for sda and, once you are satisfied that the system still boots, reverse the process. > If I'm reading some of the things I've found correctly, I might not > want to put the /boot partition in a raid cluster since grub seems to > have problems with that. If that's the case I guess I can manually > back it up as needed when new kernels get installed, perhaps using > rsync, yes? Correct to both. > I'm looking for some advice/encouragement Go for it! If I have been my usual obstruse self, feel free to ask questions. I originally did something like this several years ago, and don't repeat it often enough to be absolutely certain, so don't hesitate to point out where I drifted off track. I got most -- or all -- of this from the LVM-RAID HOWTO. Brian
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