Definition - What does Cold Server mean?
A cold server is a disaster recovery backup server that operates only if the main server is interrupted or fails. A cold server holds all main server files and programs and remains in an unpowered state until a backup is required.
Techopedia explains Cold Server
Once the appropriate software is installed on a cold server, it is turned off until it is needed. Because warm and hot servers may be cost-prohibitive, cold servers are preferred by most organizations. However, manual cold server downtime configuration is not always feasible, and a cold server demands substantial effort to bring it online. Nevertheless, this option is considerably less expensive when compared to warm and hot servers. In most cases, cold servers host low-level applications with minimal criticality.