You're welcome.
For the iMac G3 it would be an IDE WD internal HD 120GB that was installed back in 2004 by Simply Computing. I also have the 60GB IDE drive that WD replaced under warranty, still sealed in the box in case I have a major HD failure. The only issue it has is a fuzzy, not razor sharp display that could use a recalibration. Other than that, it works great. I have several FireWire drive enclosure options and of course several LaCie FireWire DVD/CD external drives. The internal CD-RW still works. And it boots Mac OS 9.
If I need any Mac OS 9 or PPC right now, I normally use my, non-originally purchased by me, Titanium 1Ghz PowerBook G4 (I need to add that to my description!).
For all the main data drives that equal the over 100TB, they are all Hitachi/WD drives both external (USB 3 is the main connection) and internal working with the Mac Pro almost exclusively. I also use a OWC 4 drive enclosure but he FireWire causes the computers to crash so I just use the USB 3 or eSata connections.
The Hitachi's are the 3TB & 4TB tanks that were the largest HD's available on the market each, when I purchased them. It pays to do the research to purchase the right drives.