Redundancy

Hard disk RAID (Redundant Array of Independent Disks) is essentially a method to span data over multiple hard disk drives with enough redundant data on all disks so that the data can be recovered from the remaining disks in case of a disk failure. Read more about RAID storage.

Data replication is a common feature of many network operating systems: file servers in the network are configured to replicate data among each other.

Tape backup is an alternative or complementing method. There are a variety of software and hardware equipment available on the market and backup policies normally include taking tapes off-site as prevention against fire or theft.

Server clustering: Many server clustering methods exist. A common one for database servers and mail servers is when two servers are working with the same storage device, commonly a RAID system. When one server fails, the other one (which is configured identically) takes over the application. These servers regularly even share the same IP address, making the so called fail-over completely transparent for the user.

Multiple video recipients: A common method to ensure disaster recovery and off-site storage in network video is to simultaneously send the video to two different servers located in separate locations. These servers can of course in their turn be equipped with RAID, work in clusters or replicate their data with servers even further away.

See also other System design considerations:

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