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Disaster Recovery Site Selection: Factors and Approach

For a Disaster Recovery strategy to work as per design, one of the important contributors is DR site as it will define service availability to customers during disasters, writes Prashant Baweja of Infosys.

Industry Perspectives

October 25, 2013

5 Min Read
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Prashant Baweja is working as a senior associate consultant with Infosys Ltd. in infrastructure domain and has a total experience of about six years.



Infosys Ltd.

Disaster recovery is an important aspect of a company’s strategy for providing uninterrupted services to its customers and end users. With a robust DR/BCP program in-place, various business outcomes can be achieved. Some of them are: improved business operations, improved performance, agility and availability, reduced disruptions and loss to business, and higher customer satisfaction.

For a DR strategy to work as per design, one of the important contributors is DR site as it will define service availability to customers during disasters. Further section details about factors to be considered for DR site selection with an approach.

Factors to Consider

DR site is very crucial for any business as it will help to keep business running in adverse scenarios. DR site selection is crucial decision as it will impact availability of services to client, RPO/RTO requirements and service performance. Some of the factors which need to be considered are:

1.Data Center Tier – Datacenter tiers are divided across Tier 1 (basic datacenter with availability of 99.67%), Tier 2 (redundant infrastructure components with availability of 99.74%), Tier 3 (has all attributes of tier1 and 2 and in addition has multiple distribution paths, dual powered etc. with availability of 99.98%) and Tier 4 (has all capabilities of prior tiers with completely redundant and highly available infrastructure and availability of 99.995%). Based on the requirement of various applications and availability, DR site tiers have to be decided.

2.Distance from Primary Data Center – Another factor which will help us determine site for DR is the distance between primary and DR site. This is crucial since it will affect latency and performance of applications.

As an illustration, if DR data center is housed at a larger distance, client will not be able to mirror data in real time in an effective manner. This will cause a risk that data will be lost if we need to switch to DR site in event of a disaster. On other hand, if distance is too small, data backup will be efficient but it will pose other threats.

3.Seismic Zone Details – Seismic zone is a region where seismic activity remains fairly constant. Each nation has divided entire area in various zones and the data is readily available in public domain. From DR site selection perspective, Primary and DR sites should be preferably in different seismic zones as it will help to curb issues arising from various seismic activities.

4.Environment Details – Next factor to consider is environment details of the area, these could be weather details, environmental hazards etc. This will help to plan out various things like resource availability, environmental cleaning mechanisms (if required), site construction and maintenance etc.

5.Third party services availability – For any datacenter site, we require to interact with a number of third parties and service providers like utilities, telecom etc. This will become more critical in case of a DR site, as the site is not up and running for 100% of the time. Two important considerations are Availability of service (whether service is available 24X7 for 365 days or for some limited period) and SLAs (what are the SLAs for the services provided by third parties? This is critical parameter as based on this, company will confirm on the SLAs with business and its customers).

6.Accessibility of Data Center – Next factor will be accessibility to DR site. This will become crucial in case disaster occurs and we need to switch operations to DR site. If the site is accessible, operations can be resumed faster. This will focus on Modes of transportation to reach DR site, Proximity to airport etc.

7.Capacity Available for Further Expansion – Capacity and scalability of DR site has to be looked into considering future growth plans.

8.Network Latency – For DR strategy to work as per requirement, data has to be copied from primary datacenter to DR. Network latency plays a major role in this and becomes a crucial factor while deciding for DR site.

9.Cost Implications – Last but not the least is cost implications of building a DR site at a particular location. This involves both CAPEX and OPEX.

Once factors are finalized for DR site selection, next action will be to select a site based on it. Next section defines about the approach for the same.

DR Site Selection – Approach

Approach for selecting a DR site is very similar to ones which we use for making most of business decisions. It includes data collection, followed by assessment and decision. Before a company starts the process of site selection for its DR Datacenter, company should have made a decision on Primary datacenter site and DR strategy is in place. Post this, below approach will help to select a site for DR Datacenter:

Step 1 – Requirement gathering: During this phase, DR strategy and policies formulated by company should be well understood. In addition to that various application requirements w.r.t. RPO/RTO and SLAs have to be collected and documented.

Step 2 – Assessment: Post data collection, next step is to assess the requirements and finalize various factors that need to be considered for site selection. Some of the above mentioned factors will help on the same.
Weighted score method can be used to work on various options that are available for DR site. Below diagram depicts an illustrative weighted score method for site selection.



Step 3 – Decision/Report: Based on analysis, weighted score method and experience, final decision need to be taken for DR site selection.

In summary, selecting a DR site is an important step in customer’s journey to build a world class infrastructure for servicing its customers. With a well-defined DR strategy and site selection process, it will become easier for companies to succeed in its business goals.

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