ReadyNAS Ultra 4 "Volume scan found errors that it could not easily correct."

Excellent, I'm in as root and have been investigating.  It seems that I keep circling around the following error:

EXT4-fs (dm-0): ext4_check_descriptors: Block bitmap for group 17216 not in group (block 623566614080)!
EXT4-fs (dm-0): group descriptors corrupted!

I found a few descriptions of a similiar problem, each mildly horrifying and all fairly dated.  Looks like I can pursue a few options

1) mke2fs - Seems the safest approach, any method to the madness?

2) Reboot without the volume check - Instructions say this is risky, but no reason given.

3) Mount with fuse and copy of the data to a new drive - All instructions point to use of ext2 which doesn't make sense to me.

4) Run fsck.ext4 - Seems I may lose data, but the disks didn't have any failures before....

5) ???

More info

# lvs
  LV   VG   Attr   LSize Origin Snap%  Move Log Copy% 
  c    c    -wi-a- 3.85T                              
# pvs
  PV         VG   Fmt  Attr PSize   PFree
  /dev/md2   c    lvm2 a-   685.12G    0 
  /dev/md3   c    lvm2 a-     3.18T 5.00G
# mount /dev/c/c /c
mount: wrong fs type, bad option, bad superblock on /dev/c/c,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

# lvscan
 ACTIVE '/dev/c/c' [3.85 TB] inherit
# cat /proc/mdstat 
Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] 
md3 : active raid5 sda6[0] sdc6[2] sdb6[1]
 3418630528 blocks super 1.2 level 5, 64k chunk, algorithm 2 [3/3] [UUU]
 
md2 : active raid5 sda5[0] sdd5[3] sdc5[5] sdb5[4]
 718431744 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]
 
md1 : active raid5 sda2[0] sdd2[3] sdc2[5] sdb2[4]
 1572672 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]
 
md0 : active raid1 sdc1[5] sdb1[4] sda1[0] sdd1[3]
 4194292 blocks super 1.2 [4/4] [UUUU]
 
unused devices: <none>