A warm site is a type of facility an organization uses to recover its technology infrastructure when its primary data center goes down. A warm site features an equipped data center but no customer data.
The warm site has some or all of the IT equipment found in a typical primary data center, such as software and hardware. After a disaster at the primary site, an organization will introduce customer data and may install additional equipment at the warm site.
A warm disaster recovery site is important for business continuity because it enables an organization to keep running in the event of an unplanned incident and prevents further data loss. Information about the site is incorporated into the organization's disaster recovery plan.
As the name suggests, a warm site is in between a hot site and a cold site. A hot site is fully functional and allows immediate recovery from a disaster while a cold site only includes infrastructure but no technology until a disaster hits.
An organization with a relatively short recovery time objective (RTO) will use a warm site, as it requires some setup, but not as much as a cold site but more than a hot site. A warm site is also a good candidate for bringing up non-essential systems that don't require the immediate restoration that mission-critical systems do.
How they work
A warm site essentially features no production work until a disaster. Servers are set up in advance, but don't contain databases. Ideally, the servers and storage at a warm site will be at least similar to the servers and storage at the primary data center, for performance and logistical benefits.
During a disaster, IT brings in the organization's backup data and any additional equipment needed to get running. The organization may pull down data from the cloud, for example using disaster recovery as a service, or use backups stored on media -- such as backup tape -- that wasn't affected by the outage at the primary data center. It's critical for an organization to know which data it will recover at the warm site -- some information is more urgent to restore.
The organization must also consider how it will bring data back to the primary data center once the disaster is over. If the organization uses the warm site for days, that could mean the creation of a large volume of data.
It's important to have necessary contact and resource information at the ready at the disaster recovery site. An organization in the middle of a recovery does not want to spend time looking for contacts or any other relevant information, especially since that material can be compiled in advance. That information is part of a disaster recovery plan.
It's also important to have a diagram of the recovery site and how it functions, plus clear directions for how to get there. An organization should be able to get in and get the business going quickly.
The disaster recovery plan, including the instructions and information for the warm site, must remain updated. Proper planning involves constantly reviewing the contents of the plan and the site itself. A test at the site is a good way to see if it will work in a recovery situation.
The warm site must be far enough away from an organization's primary data center so it's not affected by the same disaster, such as a hurricane or earthquake. To that end, it should not be on the same power grid as the primary data center. However, an organization needs to take latency issues such as network connectivity into account and make sure the site is not too far away. Location decision considerations also include staffing and cost.
Types of warm sites
A disaster recovery site is internal or external. An organization builds an internal site and owns it, while a third party owns and operates an external site.
Benefits of an internal site include management and security control. Drawbacks include cost to build it and run it. An internal site will typically provide for a quicker RTO than an external site.
At an external site, management is left to the provider. This can help an organization that lacks staffing and resources to manage the backup center.
An organization may have the external site all to itself, or it may be a colocation facility, where multiple organizations rent space. If the external site contains multiple organizations, in the event of a widespread disaster one risk is a crowded, bottlenecked space and unavailable or slower resources. At the same time, those other organizations could also provide assistance in the form of knowledge or contacts.
Another option is a mobile recovery site. This arrangement typically involves an outfitted trailer that will set up in the area of the disaster. An organization should factor in the amount of time it takes for the mobile unit to arrive at the desired location.
Warm sites vs. hot and cold sites
Considerations for deciding on a hot, warm or cold site include funding, staffing, RTO, and volume and type of data. A hot site is the costliest option while a cold site is the least expensive.
A hot site is a fully functional data center with hardware, software and customer data. It also includes staffing to manage and monitor the equipment. The hot site is ready for operation immediately following a disaster and is designed for mission-critical data and for an organization that can tolerate little to no downtime. Replication or mirroring ensures that an organization has data ready to run at a hot site. If the business is big enough and has multiple data centers, it may use one of those as a hot site. While a hot site is the most expensive option, it is also the easiest to get running.
A cold site features infrastructure to support IT, but does not have actual technology until a disaster hits and the organization brings it in. With a cold site, the organization is essentially just renting the space without equipment. It is the cheapest choice of the three, but is only for an organization or specific data that can be down for an extended period because it takes a comparatively long time to get running. An organization can also use a cold site to supplement its hot or warm site during a long-term disaster.
Though there are many differences among the three site options, they all provide a secure, off-site space for recovery, not affected by the disaster. Determining which site is best for an organization is a process that requires time, management buy-in and proper analysis of all the necessary information.