The importance of distance in a PRA

It’s almost impossible to create the perfect disaster recovery plan, which will apply to all situations and achieve all your recovery goals.

Indeed, a PRA is a continuous project that constantly needs to be adjusted. One of the things we often see as a weak point is the relative distance between the primary data center and the Disaster Recovery Site (DR).

Advantage and problem of proximity

One might think that the ideal is to have a DR site located near the main data center. It is true that the cost of a high-speed connection from site to site is lower in an urban area.

The very high speed also makes the tests, since you can use this same connection, or just around town to perform.

Ease and cost are key factors, but it is important to remember that the severity of outages varies greatly. Depending on the nature of the disaster, a nearby site may provide adequate protection. For example, a secure server or even the failure of an entire datacenter is far more common than a generalized disaster such as an extreme weather event or other regional natural disaster.

However, a single regional event can have a greater impact on the long-term viability of the company, forcing the company to close down permanently.

The reality of a regional breakdown

Your PRA planning process can face many problems if your DR site is located in the same region as the primary data center.

First, of course, the disaster will also have an impact on your DR site. Even if it is reinforced, it will work in difficult conditions, for example with diesel generators. Or even worse, it could be totally out of order.
Second, the ability of employees to access the DR site will be severely hampered as streets and public transportation are likely to be affected.

Third, in the event of a disaster, employees will first worry about their families before they become concerned about the business, and rightly so. This will include DR site staff, for example, if you rent co-location space. This staff may not be on hand to bring in your employees, in case they manage to join the site.

In addition, many roommate installations practice “overlocation”. During a regional disaster, this can lead to serious problems, as many organizations will need to access the facilities at the same time.

What is the good distance between two datacenters?

Given these concerns, it’s critical that your disaster recovery site is at a good geographic distance from your primary data center. But what is the right distance?

It is recommended that the DR site be separated from at least two regions.

In larger countries, such as the United States and Canada, it is quite easy to identify a sufficiently remote DR site. In other countries, especially in Europe, it may be difficult to distance because of the size of the country and restrictive regulations on data sovereignty.

As long as these regulations do not change, the best option for European companies may be to have two DR sites at both ends of the country in which they operate.

Tools to achieve a geographic recovery goal

The good news is that the tools to achieve a geographical recovery goal have improved significantly. Most storage systems offer native replication capabilities and some degree of application access.

If you have a second installation far enough away, you can replicate to a second, similar storage system.

There are also more than a dozen third-party replication utilities designed to protect specific applications or operating environments such as VMware . These applications often allow for point-to-point replication, so that the storage units at each site can be different.

Most of these applications push the process further by replicating to a public cloud provider such as Amazon , from a hybrid cloud perspective , which can then replicate data across multiple sites. These cloud providers will often allow you to start your applications in their cloud in the event of a disaster.

Distance is a critical element of any disaster recovery plan. Despite the benefits of a local recovery site, the risk of seeing your primary and secondary data centers hit by the same disaster is ultimately too high.

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