Expanding RAID5 from 3 1TB drives to 4

Previous config: 3 1TB drives in RAID5.

I’ve added a 4th 1TB drive, and was assuming the device would see it and automatically add it to the array. The device does see it fine (Disk Manager says the volume is fine and is “unassigned” to any volume), but does not appear to be adding it to the array. Note that this is RAID5, not span, so the autospan feature isn’t relevant here.

What do I have to do to get it to see the additional drive and expand the array?

Btw, all drives in this array are WD green power Caviar drives. No 3rd party drives.

just make sure that you used the same exact drive.  check the model number of each drive. make sure that they have exact model number.

click the link below to check


Yup, they’re all the same model. I’ve tried rebooting, but although the disk manager sees the new disk, it’s not automatically expanding the RAID to include it.