H0TF00T

Now resolved - Steps Taken
 
 
Stop array
ran gsisk /dev/sdxx over all unmountable disks after confirming GPT was corrupted binitially checking with fdisk -l /dev/sdxx (Thank you JorgeB!)
 
below process example for my /dev/sdf disk ...
 
root@Tower:/dev# gdisk /dev/sdf

GPT fdisk (gdisk) version 1.0.9.1
Caution: invalid main GPT header, but valid backup; regenerating main header
from backup!
 
Warning: Invalid CRC on main header data; loaded backup partition table.
Warning! Main and backup partition tables differ! Use the 'c' and 'e' options
on the recovery & transformation menu to examine the two tables.
Warning! Main partition table CRC mismatch! Loaded backup partition table
instead of main partition table!
 
Warning! One or more CRCs don't match. You should repair the disk!
Main header: ERROR

Backup header: OK
Main partition table: ERROR
Backup partition table: OK
Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: damaged
 
****************************************************************************
Caution: Found protective or hybrid MBR and corrupt GPT. Using GPT, but disk
verification and recovery are STRONGLY recommended.
****************************************************************************
Command (? for help): ?
b       back up GPT data to a file
c       change a partition's name
d       delete a partition
i       show detailed information on a partition
l       list known partition types
n       add a new partition
o       create a new empty GUID partition table (GPT)
p       print the partition table
q       quit without saving changes
r       recovery and transformation options (experts only)
s       sort partitions
t       change a partition's type code
v       verify disk
w       write table to disk and exit
x       extra functionality (experts only)
?       print this menu
 
Command (? for help): b
Enter backup filename to save: bupsdf.txt
The operation has completed successfully.
Command (? for help): r
Recovery/transformation command (? for help): c
Warning! This will probably do weird things if you've converted an MBR to
GPT form and haven't yet saved the GPT! Proceed? (Y/N): y
Recovery/transformation command (? for help): w
Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!
Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/sdf.
The operation has completed successfully.

root@Tower:/dev# gdisk /dev/sdf
GPT fdisk (gdisk) version 1.0.9.1
Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present
 
Rebooted server and everything is happy - running a parity check.
 
This issue arose from placing my disks in another server in attempt to migrate my Unraid setup. The new server had an Adaptec raid card and I couldn't get it to see my disks
without going through the process of trashing the data on my disks. A new install with fresh disks would have been ok. As far as I could tell. So when I placed everything back into the original machine, the disks were unmountable because of whatever the raid card did while in the intended target server.
 
Big thanks to JorgeB again!