Unable to add disk to array

I'm guessing the replacement disk you installed was not F5-supplied, correct? 
First thing I'd check is if it's being seen by the unit, do the LEDs blink? What's the output of tmsh show sys raid disk ?

Also, what procedure did you use to unmount the disk? Did you remove it from the array before switching it as detailed in https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/platform-b7000/4.html#c_reuse_fru_hd_about ? 

Thanks for the outputs.
So, let's go back to the output log in your first query. SD-A and SD-B should be the the lables of the disk in the array. In your log, it refers no ownership to SD-B so there might still be issues with "accepting" the new disk even if output shows it's present. 

Try running these commands:

dmesg |grep --color sd[a-b]
sfdisk -l /dev/sdb    # I think new disk should be seen as sdb while existing should be sda 
sfdisk -l /dev/sda

If they return disk as failed, or if they return no output, the problem is the new disk, likely. 
One more question, just fr myself to understand this better -- what was the status of the old disk that was removed? 

I'd also like to check if the linux subsystem sees the same status of the array as well .. Can you run array command too? You'll want to confront its output with the following tmsh commands (again - just to confirm again disk status)
tmsh list /sys disk all-properties   # should list both disks
tmsh show sys raid   # it's like the one I gave u last time, just has more output 

Last thing would be checking if the mdadm process is running and in sync -- but I'm not sure if it already exists in version v11, and anyways having a disk in that status will likely result in bad output for the mdadm. 

 grep -e "_U" -e "U_" -e "__" /proc/mdstat | wc -l

The error "tm_install::process::Process_array_member_add --sdb ownership is none" suggests that there may be a configuration or ownership issue with the replacement disk on your F5 7000S running OS version 11.4.1. Since the replacement disk is of a bigger capacity, it's possible that the RAID configuration is not recognizing the new disk properly. Consider updating the F5 OS to the latest available version, as newer versions may have addressed compatibility issues with different disk sizes.

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!!!

Some reall good troubleshooting here. Thanks CA_Valli.
Did you come to a conclusion/resolution/solution nycdude?

Unfortunately I have not had a chance to try anything that requires a reboot as this is our active ingress/outgress device.

We have made a choice to replace it with Netgate PFS+ since we no longer have the requirement to aggregate over 10G of througput (multiwan).

Once it is done i will try the steps on the device when it is no longer in service. I appreciate all the help here!