I just put in my 3rd 4Tb disk yesterday – and today I see

NewImage

so in 24 hours or so it has only finished around 15% of whatever it needs to do (rebuild of parity I assume) – another 2 dais until I can use the extra storage I assume.

 

 

So see the progress of the expansion, login as root via telnet or ssh and enter cat /proc/mdstat [+enter].