Glossary

Hot site

A hot site is a fully equipped secondary data center that holds current copies of production data and can take over within minutes. It is the fastest and most expensive standby option, built for workloads where an hour of downtime costs more than a second site.

Why can ransomware encrypt both sites?

A frequent surprise on the first ransomware incident: the second data center was built precisely so that one site could fail, and the malware encrypted both. A hot site keeps its data current by copying changes from production continuously, and it cannot tell a legitimate change from an attacker's. Whatever happens to the primary data, including corruption, deletion and encryption, arrives at the hot site almost as fast. The standby that protects against a flood or a power loss does not protect against this.

What makes a site hot?

A site earns the label only when three things are true at once. Capacity is running, meaning servers, storage and network are powered and sized for the production load. Data is current, meaning replication is healthy and its lag is known. And the takeover path has been exercised, meaning DNS, load balancers, identity and application configuration actually work from the second site. Losing any one of the three turns a hot site into an expensive warm one.

The replication method sets how much data is at risk. Synchronous replication confirms each write at both sites and loses nothing, but the added round-trip delay confines it to metro distances. Asynchronous replication works over any distance and leaves seconds to minutes of recent writes unreplicated, which becomes the recovery point objective.

What breaks a hot site quietly?

Configuration drift is the common one. Patches, certificates, firewall rules and new application versions get applied to production and skipped on the standby, and the difference stays invisible until takeover. Shared administrative access is the second: if one compromised account can change both sites, then a single stolen login reaches the standby too. Capacity is the third. A site that was sized correctly two years ago may no longer fit the load.

Hot, warm and cold compared by what they cost and recover

A hot site recovers in minutes, a warm site in hours to days and a cold site in days to weeks. The price follows the same order, because a hot site pays for a second complete environment all the time. Which one a system warrants comes from the business impact analysis, not from preference.

The practical pairing is a hot site for availability and an immutable backup outside the replication path, with separate credentials, for recovery from damage. The two answer different failures.

Frequently asked questions

Is a hot site the same as active-active?

Not quite. A hot site is a ready standby that takes over after a switch. In an active-active design both sites already serve users, so no switch happens.

How far apart can a hot site be?

With synchronous replication, within metro distance, since every write waits for the second site. With asynchronous replication, any distance, at the cost of some data loss.

Does a hot site need its own staff?

Not necessarily on site. Many operate with remote administration, but the runbooks, access and on-call responsibilities for takeover have to be defined and practiced.