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mort67 10-01-2007 07:23 PM

saving a raid+lvm partition on upgrade
 
I want to upgrade from FC4 to FC6 on all my linux boxes.
My Entertainment box as a lot of pictures, music and video on a raid 1 plus LVM partition.
The OS uses the first three partitions /boot,/,/swap on md0, md1, and md2. The fourth partition /video on md3 I would like to keep intact when I install FC6. Can I recover a software raid 1 plus LVM partition after installing the new OS on the first three partitions? During the installation of a new OS if I define the mount point /video and select "do not format" will the data be recovered and readable?
I have searched and understand raid 1 building and recovery. The LVM on top of raid 1 using xfs has me confused. Can a linux distribution figure all that out and use the files formed by and earlier release? I'm gussing I will have to redefine volume groups before they will be readable. As I recall the rationale for putting the OS on separate partitions from the data was to facilitate an upgrade or OS change while saving data. A pointer to how to actually do this would greatly be appreciated.
Thanks,
Mort

vonst 10-01-2007 10:04 PM

Holy cow but you've got some difficult issues. I know that when I developed my RAID 0 config, I spent a couple months trying to find answers to RAID questions. A few people helped, but mostly I performed everything thru trial and error. I didn't have LVM, because I didn't need it, but I was amazed at my ability to wipe my drives, put them back together again, REDEFINE MY PARTITIONS, and still end up with /dev/md0 having the data I started with. (Usually, I was trying to erase my install and start over again. Occasionally I would lose it all, but often, I'd repartition and then put the partitions back and then rebuild md0 and it'd be like I didn't do anything at all.)

I don't know what FC6 is, but if it's an upgrade to FC4 then you should be alright unless the Changelogs say that RAID partitions are not backwards compatible.

If I were you, tho, I'd be breaking out DVD+RW disks and copying 4 Gigs of /video files to someplace safe!

--vonSt

JimBass 10-01-2007 10:09 PM

This page has good info on how to mount/rescue a LVM partition onto a Knoppix live CD. Obviously installing Fedora is different than using a live CD, but test it out with a live CD. If it can activate and mount the volume groups, then Fedora should be able to as well. These instructions are knoppix/Debian specific, but its CLI stuff, so it probably will work regardless of what live CD you try it with.

http://www.knoppix.net/wikinew/index.php?title=LVM2

I've mounted LVM partitions this way, but never software RAID1 too. RAID1 shouldn't be a big deal, as the data is mirrored. Even if the live CD sees it as 2 separate units, just mount the first, then remove the 2nd from the software RAID, then re-add it and it will be mirrored from the first. RAID0 would be more tricky I suspect.

Peace,
JimBass

mort67 10-02-2007 10:03 AM

thanks for reply
 
I'll just try an os install and lrt you know what happens.


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