Linux Client, error on creating LVM snapshot

Server
1

The backup is working the same though, but I keep getting LVM creating error:
Creating snapshot of "/var/www/directory1" failed
Volume group "md2" not found
Skipping volume group md2
Could not find LVM volume group of volume /dev/mapper/md2
Creating snapshot of "directory1" failed.
Creating snapshot of "/var/www/directory2" failed
Volume group "md2" not found
Skipping volume group md2
Could not find LVM volume group of volume /dev/mapper/md2
Creating snapshot of "directory2" failed.
Creating snapshot of "/var/www/directory3" failed
Volume group "md2" not found
Skipping volume group md2
Could not find LVM volume group of volume /dev/mapper/md2
Creating snapshot of "directory3" failed.
Creating snapshot of "/var/www/directory4" failed
Volume group "md2" not found
Skipping volume group md2
Could not find LVM volume group of volume /dev/mapper/md2
Creating snapshot of "directory4" failed.

Last version of linux client on debian wheezy.

File system     Dim. Usati Dispon. Uso% Montato su
     rootfs          1,8T  816G    925G  47% /
     udev             10M     0     10M   0% /dev
     tmpfs           3,2G  244K    3,2G   1% /run
     /dev/md2        1,8T  816G    925G  47% /
     tmpfs           5,0M     0    5,0M   0% /run/lock
     tmpfs           6,5G     0    6,5G   0% /dev/shm

I edited the file for creating snapshot, cause was configured to create a snapshot of 150% free space. Cause I don’t need all of this, the “data” is like 110GB, I fix the variable to 150G
SNAP_SIZE="-L150G"

What is going on?

2

/dev/md* usually is a Software RAID device, not LVM, so LVM snapshots won’t work directly with it (you’d need to put LVM on top of md dev).

3

Can you help me please? I cannot quite understand what you are saying here…
thanks for help

btw the backups are running, can be a problem that lvm does not work? Can I leave it with it?