Unable to add disk to array

Thank you CA_Valli, i really appreciate your responses.

About original hard drive - when we had DC outage (complete power failure) the device restarted and basically showed No disk in bay 2 (Despite the disk being there). When i did the commands to check array status with the old disk still inserted it confirmed that the device was not seeing it in either TMOS or BSH. (I have had disks fail like that in PC's where it was spinning and powered but not visible to OS).

Here are the outputs:

[:Active:Standalone] ~ # dmesg |grep --color sd[a-b]
sd 1:0:0:0: [sda] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB)
sd 1:0:0:0: [sda] 4096-byte physical blocks
sd 1:0:0:0: [sda] Write Protect is off
sd 1:0:0:0: [sda] Mode Sense: 00 3a 00 00
sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
sda: sda1 sda2
sd 1:0:0:0: [sda] Attached SCSI disk
md: bind<sda1>
md: could not bd_claim sda1.
sd 0:0:0:0: [sdb] 3907029168 512-byte logical blocks: (2.00 TB/1.81 TiB)
sd 0:0:0:0: [sdb] Write Protect is off
sd 0:0:0:0: [sdb] Mode Sense: 00 3a 00 00
sd 0:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
sdb: unknown partition table
sd 0:0:0:0: [sdb] Attached SCSI disk
sdb: unknown partition table
sdb:
[:Active:Standalone] ~ # sfdisk -l /dev/sdb

Disk /dev/sdb: 243201 cylinders, 255 heads, 63 sectors/track
Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

Device Boot Start End #cyls #blocks Id System
/dev/sdb1 0 - 0 0 0 Empty
/dev/sdb2 0 - 0 0 0 Empty
/dev/sdb3 0 - 0 0 0 Empty
/dev/sdb4 0 - 0 0 0 Empty
[:Active:Standalone] ~ #

(cfg-sync Standalone)(Active)(/Common)(tmos)# list /sys disk all-properties
sys disk application-volume afmdata {
logical-disk MD1
owner afm
preservability precious
resizeable false
size 3900
volume-set-visibility-restraint none
}
sys disk application-volume avrdata {
logical-disk MD1
owner avr
preservability precious
resizeable false
size 3900
volume-set-visibility-restraint none
}
sys disk application-volume mysqldb_MD1.1 {
logical-disk MD1
owner mysql
preservability precious
resizeable false
size 12288
volume-set-visibility-restraint MD1.1
}
sys disk logical-disk HD1 {
mode control
size 953869
vg-free 867148
vg-in-use 85784
vg-reserved 40
}
sys disk logical-disk HD2 {
mode none
size 1907729
vg-free 0
vg-in-use 0
vg-reserved 30720
}
sys disk logical-disk MD1 {
mode mixed
size 953869
vg-free 863192
vg-in-use 89740
vg-reserved 30720
}
(cfg-sync Standalone)(Active)(/Common)(tmos)#

(cfg-sync Standalone)(Active)(/Common)(tmos)# show sys raid

---------------------
Sys::Raid::Array: MD1
---------------------
Size (MB) 931.5K

---------------------------------------------------------
Sys::Raid::ArrayMembers
Bay ID Serial Number Name Array Member Array Status
---------------------------------------------------------
1 WD-WXR1E63HMUYD HD1 yes ok

-------------------------------------------------------------
Sys::Raid::Bay
Bay Shelf Name Serial Number Array Member Array Status
-------------------------------------------------------------
1 1 HD1 WD-WXR1E63HMUYD yes ok
2 1 HD2 S6PNNJ0W412826X no undefined

---------------------------------------------------------------------
Sys::Raid::Disk
Name Serial Number Array Array Status Model
Member
---------------------------------------------------------------------
HD1 WD-WXR1E63HMUYD yes ok ATA WDC WD1000CHTZ-0
HD2 S6PNNJ0W412826X no undefined ATA Samsung SSD 870

(cfg-sync Standalone)(Active)(/Common)(tmos)#

[Active:Standalone] ~ # grep -e "_U" -e "U_" -e "__" /proc/mdstat | wc -l
19

Thanks again and very much appreciated!!!