erreur au montage d'un disque en raid + lvm

montage du disque dans un boîtier usb
=====================================
# mdadm --assemble --scan
mdadm: /dev/md1 has been started with 1 drive (out of 2).
mdadm: /dev/md2 has been started with 1 drive (out of 2).
# pvscan
   PV /dev/md2   VG main   lvm2 [232,78 GiB / 0    free]
   Total: 1 [232,78 GiB] / in use: 1 [232,78 GiB] / in no VG: 0 [0   ]
# vgscan
   Reading all physical volumes.  This may take a while...
# lvscan
   inactive          '/dev/main/root' [228,84 GiB] inherit
   inactive          '/dev/main/swap' [3,94 GiB] inherit
# lvchange -ay /dev/main/root
# lvscan
   ACTIVE            '/dev/main/root' [228,84 GiB] inherit
   inactive          '/dev/main/swap' [3,94 GiB] inherit
# lvs
   LV   VG   Attr     LSize   Pool Origin Data%  Move Log Copy%  Convert
   root main -wi-a--- 228,84g
   swap main -wi-----   3,94g
# mount /dev/main/root /media/dd-sylvain
mount: wrong fs type, bad option, bad superblock on /dev/mapper/main-root,
        missing codepage or helper program, or other error
        In some cases useful info is found in syslog - try
        dmesg | tail  or so
# dmesg | tail -20
[232802.411129] md: md1 stopped.
[232802.475580] md: bind<sdb1>
[232802.516885] bio: create slab <bio-1> at 1
[232802.519479] md/raid1:md1: active with 1 out of 2 mirrors
[232802.519548] md1: detected capacity change from 0 to 106823680
[232802.523160]  md1:
[232802.836882] md: md2 stopped.
[232802.874151] md: bind<sdb2>
[232802.948130] md/raid1:md2: active with 1 out of 2 mirrors
[232802.948199] md2: detected capacity change from 0 to 249949716480
[232802.956263]  md2: unknown partition table
[233107.466625] sd 1:0:0:0: [sdb] Unhandled sense code
[233107.466639] sd 1:0:0:0: [sdb]  Result: hostbyte=DID_OK 
driverbyte=DRIVER_SENSE
[233107.466651] sd 1:0:0:0: [sdb]  Sense Key : Medium Error [current]
[233107.466664] sd 1:0:0:0: [sdb]  Add. Sense: Data phase error
[233107.466680] sd 1:0:0:0: [sdb] CDB: Read(10): 28 00 00 06 37 ed 00 00 
f0 00
[233107.466705] end_request: I/O error, dev sdb, sector 407533
[233107.466842] JBD: Failed to read block at offset 22707
[233110.499057] JBD: recovery failed
[233110.499075] EXT3-fs (dm-0): error loading journal

démontage du disque dur
=======================
# vgchange -an /dev/main
   0 logical volume(s) in volume group "main" now active
# vgs
   VG   #PV #LV #SN Attr   VSize   VFree
   main   1   2   0 wz--n- 232,78g    0
# lvs
   LV   VG   Attr     LSize   Pool Origin Data%  Move Log Copy%  Convert
   root main -wi----- 228,84g
   swap main -wi-----   3,94g
# lvscan
   inactive          '/dev/main/root' [228,84 GiB] inherit
   inactive          '/dev/main/swap' [3,94 GiB] inherit
# mdadm --stop --scan
mdadm: stopped /dev/md2
mdadm: stopped /dev/md1