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I am rebuilding my Ubuntu home server, but I want to preserve my two disks currently in Linux software RAID 1.

My current config is:

One 240GB HDD configured as OS Disk (Ubuntu 12.04 LTS) Two 3TB WD Reds configured as Linux RAID 1 - contains home files, pictures, videos, backups, etc

For a number of reasons, I need to re-build the system on a new OS Disk with Ubuntu 14.04.1 LTS, which will be a 240GB SSD. With the new system, is there a way to mount the two RAID drives without (a) losing data and (b) needing to rebuild the RAID array?

Thanks!

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Based on David Foerster's answer, I moved forward. I was able to successfully migrate the RAID volume. One detail that complicated the move was that I had the RAID array as part of the LVM Group. So once I had the new system re-built, the RAID array was recognized, but I was unable to mount any of the LVMs.

I ended up having to use vgexport/vgimport to export and import the volume group. It is a good thing I was installing to a new OS Disk, meaning I still had my old OS disk, which allowed me to revert back and properly export LVMs. The procedure I followed is here on tldp.org(except this is missing the deactivation and reactivation of logical volumes).

My original configuration was:

  1. 2x3TB Disks in Linux RAID1 with a single Ext4 partition for file storage data (no OS).
  2. 3TB RAID array added as the sole device within volume: /dev/NASRaid1/NAS_LVM
  3. /dev/NASRaid1/NAS_LVM mounted to filesystem as /nfs

Steps taken to export and import the volume were:

  1. Unmount filesystem(s): unmount /nfs (I also had an export mirror for a Samba share that I had to un-mount as well)
  2. Deactivate logical volume(s): lvchange -an /dev/NASRaid1/NAS_LVM
  3. Deactivate volume group: vgchange -an NASRaid1
  4. Export the volume group: vgexport NASRaid1
  5. Add RAID Array to new system and boot up. Running pvscan lists the exported volume group(s).
  6. Import the volume group: vgimport NASRaid1
  7. Activate the volume group: vgchange -ay NASRaid1
  8. Activate the volume(s): lvchange -ay /dev/NASRaid1/NAS_LVM
  9. Mount the filesystem(s): mkdir -p /nfs; mount /dev/NASRaid1/NAS_LVM /nfs

Worked like a charm.

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mdadm stores all the necessary info to reassemble a RAID in the volume header. As soon as you configure it correctly in your new system it should pick up the existing volumes.

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