RAID
Redundant Array of Inexpensive/Independent Disks; A storage mechanism using multiple disks, designed to increase performance and protect against loss of data
eSATA
External Serial Advanced Attachment Interface; A connection using SATA interfaces and designed for supporting externally attached disk drives
NAS
Network Attached Storage; A file-level storage system that is accessible across a TCP/IP network
SAN
Storage Area Network; A block-level storage system that frequently uses a dedicated network to provide backup and storage services