The Apple Drive Module (ADM) is a hot-pluggable Serial ATA hard drive in a special drive carrier module designed for easy server upgradeability and maintenance. Apple Drive Modules operate at 7200 rpm and are equipped with 8MB disk cache.Using up to three 80GB or 250GB ADMs, the Xserve G5 can be configured from 80 to 750 gigabytes of internal storage. Unpopulated bays ship with a blank drive carrier which can be replaced with a drive module at any time - even if the server is running - so its easy to add storage capacity as your server needs grow.