As shipped, the server's internal hard drives are configured as multipath (mpxio) devices, and you must issue the cfgadm unconfigure command for both paths to the drive before removing it. After unconfiguring the first path to the drive, the blue OK to Remove LED illuminates. Do not remove the drive at this time. It is not safe to remove the drive until the second path has been unconfigured.
Workaround: Do not rely upon the blue OK to Remove LED for permission to remove the hard drive. Instead, use the cfgadm -al or format commands to verify that both paths have been unconfigured, and that it is truly safe to remove the drive.