I recently replaced my Parity drive with a 4TB Seagate drive.  Since installing I have noticed the activity light stays lit up.  When I had all WD reds and greens the activity light worked great.  I have read some old posts that upgrading the firmware could fix it.  Is it possible to do this without data loss?  Do I have to pull the drive to do it?

AFAIK updating drive firmware shouldn't lead to data loss.  I'd run a parity check, then if everything is good, shut down, pull the drive, update the firmware in another system, and put it back.  After it's booted back up do a non correcting parity check.

 

If there are any issues you then just have to rebuild parity.

 

If there are any issues you then just have to rebuild parity.

 

Actually, if there are any issues, it's much more likely you'll need to rebuild the drive -- NOT parity. 

 

... but I can't imagine any reason why that would be the case.    Updating the firmware won't change the drive's serial number or its size ... and those are the only things that would cause an issue.