They are almost exclusively for usage in servers that use hot swappable (hot-swap) drives with a SAS hot pluggable backplane. You use a hard drive tray or caddy or sled, and simply slide and clip the drive into the front of your server.

 If a drive in a storage array fails, the system uses a redundant drive. Hot swappable drives are identified with a purple tab.

Hot swap storage drives usually come with a RAID (Redundant Array of Independent Disks) setup. A RAID utilizes multiple drives simultaneously for data redundancy, increased reliability, and improved performance. It works by mirroring or duplicating data on two separate drives or splitting the data across multiple devices. Thus, the RAID setup provides data redundancy when one of the drives is hot swapped to ensure no corrupted data during the process.