The hard drives in the server are hot-pluggable, but this capability depends on how the hard drives are configured. To hot-plug a drive you must take the drive offline before you can safely remove it. Taking a drive offline prevents any applications from accessing it, and removes the logical software links to it.
Caution - You must use hard drives designed for this server, which have a vented front panel to allow adequate airflow to internal system components. Installing inappropriate hard drives could result in an overtemperature condition.
If the hard drive contains the operating system, and the operating system is not mirrored on another drive.
If the hard drive cannot be logically isolated from the online operations of the server.
If your drive falls into one of these conditions, you must power off the server before you replace the hard drive.