Пробовал на debian7, ubuntu12.04 server LTS, ubuntu13.04 server. В общем есть 2 lvm-раздела: /dev/sda2 и /dev/sdb2, на sda2 создан системный раздел logical volume ha2_2/root. Volume group ha2_2 расширена на /dev/sdb2 (vgextend ha2_2 /dev/sdb2). Далее мирорим (lvconvert -m1 --corelog ha2_2/root /dev/sdb2) и в результате имеем (для 12.04 lts):
root@ha2-node2:~# lvm version
LVM version: 2.02.66(2) (2010-05-20)
Library version: 1.02.48 (2010-05-20)
Driver version: 4.23.1
-------------------
root@ha2-node2:~# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 ha2_2 lvm2 a- 931.27g 921.96g
/dev/sdb2 ha2_2 lvm2 a- 931.27g 921.96g
-------------------
root@ha2-node2:~# vgs
VG #PV #LV #SN Attr VSize VFree
ha2_2 2 1 0 wz--n- 1.82t 1.80t
---------------------
root@ha2-node2:~# lvs -a -o name,devices,size
LV Devices LSize
root root_mimage_0(0),root_mimage_1(0) 9.31g
[root_mimage_0] /dev/sda2(0) 9.31g
[root_mimage_1] /dev/sdb2(0) 9.31g
root@ha2-node2:~# echo "1" > /sys/bus/scsi/devices/target2\:0\:0/2\:0\:0\:0/delete
INFO: task jbd2/dm-2-8:347 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
INFO: task rs:main Q:Reg:893 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
...
