Cant Add HDD to existing RAID-5

I think he is talking about expanding the RAID 5, not replacing a failed member.

According to the picture you posted, it should be ready to go. A couple of things that will prevent it:

• Disk is not the right size - must be equal to or larger (keep in mind that even marketed sizes between models and manufacturers can vary enough to prevent using a disk of the same "size" from working).
• Disk is not compatible - happens less frequently with SAS than SATA, but if it is not a Dell-certified drive, it may not communicate properly with the controller and can't be used.
• You have multiple VD's configured across the same set of disks - this cannot be done; you would need to first delete the second VD, expand it by adding a disk, then set up the second VD and restore from backup.

Thanks the flash1932!

Have you been able to verify the suggestions provided by the Flash1932? If you may, provide screenshot of the VD and the part number of one of the old drives and the new drive so that we look up more information.

The size of the drive is a terabyte.  Same make of the existing ones.  revision is different.  existing ones are HTF2 the new one is AS08.  It wont see it when i try and reconfigure.  

Expand a disk with the HTF2 firmware and provide a screenshot, then expand the disk with the AS08 firmware and provide a screenshot of that.

Go to the Virtual Disks page and provide a screenshot of that.

ok let me do that

AS08

Virtual Disk

Same make of the existing ones.  revision is different.

No, they aren't the same at all. They are both Seagate drives, but:

• The smaller ones are the Seagate Savvio SAS drives
• The larger/new one is a Seagate Constellation NearLine SAS drive
• The Savvio is 15K RPM, the Constellation is 7.2K RPM
• The Savvio supports SED (self encryption), the Constellation does not

Is the new one a Dell-certified drive? Just because they are both Seagate doesn't mean they will work well together. Even if they are all certified, they are still very different drives and likely why you can't put them in the same array together. I would strongly recommend getting a certified 15K SED SAS drive to add to the array. Even if it worked, I wouldn't recommend you use it.

https://velocitytechsolutions.com/dell-u733k-hard-drive-146gb-15k-sas-2-5-in-tray/