What is a cold backup?
A cold backup, also known as an offline backup, is a database backup during which the database is offline and not accessible for updating. This is the safest way to back up because it avoids the risk of copying data that may be updating. However, a cold backup involves downtime because users cannot access the database during the backup.
A cold backup can be performed on another disk of the server where the database resides. However, if the server goes down, the backup will also disappear. To avoid this problem, the cold data backup is often copied to tape or disk on another server.
A USB flash drive or external hard drive can also undergo a cold backup by unplugging the drive after the backup. However, the USB drive or external hard drive must be reconnected for each subsequent backup.
Benefits of cold backup
Cold backups are immune to power surges and interruptions and cannot be interrupted by a virus or intruder. Plus, cold data backups prevent accidental overwrites or deletions.
A cold backup guarantees a consistent backup, but cannot be used for systems that require continuous 24/7 operation. No user should be logged in and no activity should take place to ensure that the files remain unchanged during the backup.
If an organization backs up data to an offsite facility, it can perform cold backups from a copy of the data. Data files do not change during a cold backup process, ensuring that the database is in a consistent state when it returns to normal operation. Cold backup servers are disabled until a disaster event occurs and users must enter disaster recovery mode.
Cold Backup vs. Hot Backup vs. Hot Backup
Cold backup sites are inexpensive to maintain. They are little more than a properly configured space in a building where everything needed to render service to users must be procured and then delivered to site before the recovery process can begin. The time involved in bringing a cold data backup site to full operation can be long. When system downtime needs to be minimized, a hot backup can provide an alternative to a cold backup.
A hot backup can be performed even when users are accessing the database, but if the data changes during the backup, it may be inconsistent. A hot backup can also impact database performance because it uses compute resources. Hot backup servers typically receive continuous updates from the production server and are ready to take over whenever a failover event brings the production server down.
In a hot backup, the server is powered on but not doing any work, or it is powered on occasionally to get updates from the server being backed up. Hot backups are typically used for mirroring or replication.