HP StorageWorks 500 G2 Modular Smart Array - Manual (Page 25)

Component identification 25
Activity
LED (1) Online
LED (2) Fault LED
(3) Interpretation
Off Off Off Either (1) the drive is not configured as part of an array; (2) the drive
is configured as part of an array, but it is a replacement drive that is
not being accessed or being rebuilt yet; or (3) the drive is configured
as an online spare.
If the drive is connected to an array controller, you may replace the
drive online.