I am having a hard time believing that. I also encountered that message on my Proliant 6000, and the complete text is:
Compaq Drive Array Physical Drive Threshold Exceeded. The physical drive in slot 9, port 2, bay 4 with serial number "WT7060300259", has exceeded a drive threshold.
[SNMP TRAP: 3030 in CPQIDA.MIB]
The drive specified in the above message is one 18.2 GB drive out of a RAID 5-array with 11 drives (plus one hot spare). "Filling" only makes sense with regard to the complete RAID-array, not regarding a single drive in it. There must be a better explanation.