Hot-Swap
The ability to remove and insert drives while the system is powered on, without shutting down.
Hot-swap bays make replacing a failed drive in a RAID or ZFS pool painless — you pull the dead disk and slot in a new one while the array keeps serving data and rebuilds in the background.
Related articles
RAID(Redundant Array of Independent Disks)
A method of combining multiple drives so they act as one, improving performance and/or protecting against drive failure.
NAS(Network-Attached Storage)
A dedicated storage device connected to your network that lets multiple devices store and access files centrally.
HDD(Hard Disk Drive)
A spinning magnetic drive offering large capacity at a low price per terabyte.