Reusing Raid 5 Drive?

These servers are from 2004 and 2002, respectively (The DL380 G2 is a Pentium 3 system, while the ML530 G2 is a Pentium 4 Xeon server). Both use standard Ultra 3 or Ultra 320 SCSI hard drives. You do not need to do anything special to reuse the disk.

You did not specify which system's disks were going where, but both servers should have Smart Array controllers within a generation of each other. The Smart Array RAID controller will take care of the drive initialization when you add it to the array.

There's nothing else needed to make the used drive work.

It should be fine to put the drive in. Assuming it's still running one of the SmartArray controllers, it should start to rebuild the array on it's own. The array should see it as a replacement - worst case is you go into the array manager and tell it manually start rebuilding the array.