Dump a partition with fsarchiver

fsarchiver

# http://www.fsarchiver.org/QuickStart
sudo apt-get install fsarchiver

# Find out what partition is used for the current folder and choose another partition for the dump
df -h .
df -h

# Re-mount /dev/md2 partition to read only mode
sudo mount -o remount,ro /dev/md2
sudo fsarchiver savefs ./ubuntu-md2.fsa /dev/md2

# Force dump in case you can't set read-only mode
sudo fsarchiver -A savefs ./ubuntu-md2.fsa /dev/md2

# Restore the dump
fsarchiver restfs ./ubuntu-md2.fsa id=0,dest=/dev/md2