Disaster recovery

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Disaster recovery involves a set of policies, tools and procedures to enable the recovery or continuation of vital technology infrastructure and systems following a natural or human-induced disaster. Disaster recovery focuses on the IT or technology systems supporting critical business functions,[1] as opposed to business continuity, which involves keeping all essential aspects of a business functioning despite significant disruptive events. Disaster recovery can therefore be considered as a subset of business continuity.[2][3]

IT Service Continuity[edit]

IT Service Continuity[4][5] (ITSC) is a subset of Business Continuity Planning (BCP)[6] and encompasses IT disaster recovery planning and wider IT resilience planning. It also incorporates those elements of IT infrastructure and services which relate to communications such as (voice)telephony and data communications.

The ITSC Plan reflects Recovery Point Objective (RPO - recent transactions) and Recovery Time Objective (RTO - time intervals).

Principles of Backup sites[edit]

Planning includes arranging for backup sites, be they hot, warm, cold or standby sites with hardware as needed for continuity.

In 2008 the British Standards Institution launched a specific standard connected and supporting the Business Continuity Standard BS 25999 titled BS25777 specifically to align computer continuity with business continuity. This was withdrawn following the publication in March 2011 of ISO/IEC 27031 - Security techniques — Guidelines for information and communication technology readiness for business continuity.

ITIL® has defined some of these terms.[7]

Recovery time objective[edit]

The recovery time objective (RTO)[8][9] is the targeted duration of time and a service level within which a business process must be restored after a disaster (or disruption) in order to avoid unacceptable consequences associated with a break in business continuity.[10]

Schematic representation of the terms RPO and RTO. In this example, the agreed values of RPO and RTO are not fulfilled.

In accepted business continuity planning methodology, the RTO is established during the Business Impact Analysis (BIA) by the owner of a process, including identifying options time frames for alternate or manual workarounds.

In a good deal of the literature on this subject, RTO is spoken of as a complement of recovery point objective (RPO), with the two metrics describing the limits of acceptable or "tolerable" ITSC performance in terms of time lost (RTO) from normal business process functioning, and in terms of data lost or not backed up during that period of time (RPO) respectively.[10][11]

Recovery time actual[edit]

A Forbes overview[8]noted that it is recovery time actual(RTA) which is "the critical metric for business continuity and disaster recovery."

RTA is established during exercises or actual events. The business continuity group times rehearsals (or actuals) and makes needed refinements.

Recovery point objective[edit]

A recovery point objective (RPO) is defined by business continuity planning. It is the maximum targeted period in which data (transactions) might be lost from an IT service due to a major incident.[10]

If RPO is measured in minutes (or even a few hours),then in practice, off-site mirrored backups must be continuously maintained – a daily off-site backup on tape will not suffice.[12]

Schematic representation of the terms RPO and RTO. In this example, the agreed values of RPO and RTO are not fulfilled.

Relationship to recovery time objective (RTO)[edit]

Recovery that is not instantaneous will restore data/transactions over a period of time; the goal is without incurring significant risks or significant losses.[10]

RPO measures the maximum time period in which recent data might have been permanently lost in the event of a major incident; it is not a direct measure of the quantity of such loss. For instance if the BC plan is "restore up to last available backup", the RPO is the maximum interval between such backup that has been safely vaulted offsite.

Two points should be noted. Firstly, business impact analysis is used to determine RPO for each service – RPO is not determined by the existent backup regime. Secondly, when any level of preparation of off-site data is required, the period during which data often starts near the time of the beginning of the work to prepare backups, not the time the backups are taken off-site.

Data synchronization points[edit]

Although a data synchronization point[13] is a point in time, the timing for performing the physical backup must be included. One approach used is to halt processing of an update queue, while a disk-to-disk copy is made. The backup[14] reflects the earlier time of that copy operation, not when the data is copied to tape or transmitted elsewhere.

How RTO and RPO values affect computer system design[edit]

RTO and the RPO must be balanced, along with all the other major system design criteria.[15]

RPO is tied to the times backups are sent offsite. Offsiting via synchronous copies to an offsite mirror allows for most unforeseen difficulty. Use of physical transportation for tapes (or other transportable media) comfortably covers some backup needs at a relatively low cost. Recovery can be enacted at a predetermined site. Shared offsite space and hardware completes the package needed.[citation needed]

For high volumes of high value transaction data, the hardware can be split across two or more sites; splitting across geographic areas adds resiliency.


Planning for disaster recovery and information technology (IT) developed in the mid- to late 1970s as computer center managers began to recognize the dependence of their organizations on their computer systems.

At that time, most systems were batch-oriented mainframes. Another offsite mainframe could be loaded from backup tapes pending recovery of the primary site; downtime was relatively less critical.

The disaster recovery industry[16][17] developed to provide backup computer centers. One of the earliest such centers was located in Sri Lanka (Sungard Availability Services, 1978).[citation needed]

During the 1980s and 90s, as internal corporate timesharing, online data entry and real-time processing grew, more availability of IT systems was needed.

Regulatory agencies became involved even before the rapid growth of the Internet during the 2000s; objectives of 2, 3, 4 or 5 nines (99.999%) were often mandated, and high-availability solutions for hot-site facilities were sought.[citation needed]

IT Service Continuity is essential for many organizations in the implementation of Business Continuity Management (BCM) and Information Security Management (ICM) and as part of the implementation and operation information security management as well as business continuity management as specified in ISO/IEC 27001 and ISO 22301 respectively.

The rise of cloud computing since 2010 continues that trend: nowadays, it matters even less where computing services are physically served, just so long as the network itself is sufficiently reliable (a separate issue, and less of a concern since modern networks are highly resilient by design). 'Recovery as a Service' (RaaS) is one of the security features or benefits of cloud computing being promoted by the Cloud Security Alliance.[18]

Classification of disasters[edit]

Disasters can be classified into two broad categories. The first is natural disasters such as floods, hurricanes, tornadoes or earthquakes. While preventing a natural disaster is impossible, risk management measures such as avoiding disaster-prone situations and good planning can help. The second category is man-made disasters, such as hazardous material spills, infrastructure failure, bio-terrorism, and disastrous IT bugs or failed change implementations. In these instances, surveillance, testing and mitigation planning are invaluable.

Importance of disaster recovery planning[edit]

Recent research supports the idea that implementing a more holistic pre-disaster planning approach is more cost-effective in the long run. Every $1 spent on hazard mitigation(such as a disaster recovery plan) saves society $4 in response and recovery costs.[19]

2015 disaster recovery statistics suggest that downtime lasting for one hour can cost

  • small companies as much as $8,000,
  • mid-size organizations $74,000, and
  • large enterprises $700,000.[20]

As IT systems have become increasingly critical to the smooth operation of a company, and arguably the economy as a whole, the importance of ensuring the continued operation of those systems, and their rapid recovery, has increased. For example, of companies that had a major loss of business data, 43% never reopen and 29% close within two years. As a result, preparation for continuation or recovery of systems needs to be taken very seriously. This involves a significant investment of time and money with the aim of ensuring minimal losses in the event of a disruptive event.[21]

Control measures[edit]

Control measures are steps or mechanisms that can reduce or eliminate various threats for organizations. Different types of measures can be included in disaster recovery plan (DRP).

Disaster recovery planning is a subset of a larger process known as business continuity planning and includes planning for resumption of applications, data, hardware, electronic communications (such as networking) and other IT infrastructure. A business continuity plan (BCP) includes planning for non-IT related aspects such as key personnel, facilities, crisis communication and reputation protection, and should refer to the disaster recovery plan (DRP) for IT related infrastructure recovery / continuity.

IT disaster recovery control measures can be classified into the following three types:

  1. Preventive measures – Controls aimed at preventing an event from occurring.
  2. Detective measures – Controls aimed at detecting or discovering unwanted events.
  3. Corrective measures – Controls aimed at correcting or restoring the system after a disaster or an event.

Good disaster recovery plan measures dictate that these three types of controls be documented and exercised regularly using so-called "DR tests".


Prior to selecting a disaster recovery strategy, a disaster recovery planner first refers to their organization's business continuity plan which should indicate the key metrics of recovery point objective (RPO) and recovery time objective (RTO) for various business processes (such as the process to run payroll, generate an order, etc.)[22]. The metrics specified for the business processes are then mapped to the underlying IT systems and infrastructure that support those processes.[23]

Incomplete RTOs and RPOs can quickly derail a disaster recovery plan. Every item in the DR plan requires a defined recovery point and time objective, as failure to create them may lead to significant problems that can extend the disaster’s impact.[24] Once the RTO and RPO metrics have been mapped to IT infrastructure, the DR planner can determine the most suitable recovery strategy for each system. The organization ultimately sets the IT budget and therefore the RTO and RPO metrics need to fit with the available budget. While most business unit heads would like zero data loss and zero time loss, the cost associated with that level of protection may make the desired high availability solutions impractical. A cost-benefit analysis often dictates which disaster recovery measures are implemented.

Traditionally, a disaster recovery system involved cutover or switch-over recovery systems.[citation needed] Such measures would allow an organization to preserve its technology and information, by having a remote disaster recovery location that produced backups on a regular basis. However, this strategy proved to be expensive and time-consuming. Therefore, more affordable and effective cloud-based systems were introduced.

Some of the most common strategies for data protection include:

  • backups made to tape and sent off-site at regular intervals
  • backups made to disk on-site and automatically copied to off-site disk, or made directly to off-site disk
  • replication of data to an off-site location, which overcomes the need to restore the data (only the systems then need to be restored or synchronized), often making use of storage area network (SAN) technology
  • Private Cloud solutions which replicate the management data (VMs, Templates and disks) into the storage domains which are part of the private cloud setup. These management data are configured as an xml representation called OVF (Open Virtualization Format), and can be restored once a disaster occurs.
  • Hybrid Cloud solutions that replicate both on-site and to off-site data centers. These solutions provide the ability to instantly fail-over to local on-site hardware, but in the event of a physical disaster, servers can be brought up in the cloud data centers as well.
  • the use of high availability systems which keep both the data and system replicated off-site, enabling continuous access to systems and data, even after a disaster (often associated with cloud storage)[25]

In many cases, an organization may elect to use an outsourced disaster recovery provider to provide a stand-by site and systems rather than using their own remote facilities, increasingly via cloud computing.

In addition to preparing for the need to recover systems, organizations also implement precautionary measures with the objective of preventing a disaster in the first place. These may include:

  • local mirrors of systems and/or data and use of disk protection technology such as RAID
  • surge protectors — to minimize the effect of power surges on delicate electronic equipment
  • use of an uninterruptible power supply (UPS) and/or backup generator to keep systems going in the event of a power failure
  • fire prevention/mitigation systems such as alarms and fire extinguishers
  • anti-virus software and other security measures


Several large hardware vendors have developed mobile/modular solutions that can be installed and made operational in very short time.

A modular data center connected to the power grid at a utility substation

See also[edit]


  1. ^ Systems and Operations Continuity: Disaster Recovery. Georgetown University. University Information Services. Retrieved 3 August 2012.
  2. ^ Disaster Recovery and Business Continuity, version 2011. Archived January 11, 2013, at the Wayback Machine. IBM. Retrieved 3 August 2012.
  3. ^ [1] 'What is Business Continuity Management', DRI International, 2017
  4. ^ M. Niemimaa; Steven Buchanan (March 2017). "Information systems continuity process". ACM.com (ACM Digital Library).
  5. ^ "2017 IT Service Continuity Directory" (PDF). Disaster Recovery Journal.
  6. ^ "Defending The Data Strata". ForbesMiddleEast.com. December 24, 2013.
  7. ^ "ITIL® glossary and abbreviations".
  8. ^ a b "Like The NFL Draft, Is The Clock The Enemy Of Your Recovery Time". Forbes. April 30, 2015.
  9. ^ "Three Reasons You Can't Meet Your Disaster Recovery Time". Forbes. October 10, 2013.
  10. ^ a b c d "Understanding RPO and RTO" Druva, 2008. Retrieved 2013-2-13.
  11. ^ http://searchstorage.techtarget.com/feature/What-is-the-difference-between-RPO-and-RTO-from-a-backup-perspective
  12. ^ Richard May. "Finding RPO and RTO". Archived from the original on 2016-03-03.
  13. ^ "Data transfer and synchronization between mobile systems". May 14, 2013.
  14. ^ "Amendment #5 to S-1". SEC.gov. real-time ... provide redundancy and back-up to ...
  15. ^ Data Center Availability report 2014. Veeam Software.
  16. ^ "Catastrophe? It Can't Possibly Happen Here". The New York Times. January 29, 1995. .. patient records
  17. ^ "Commercial Property/Disaster Recovery". NYTimes.com. October 9, 1994. ...the disaster-recovery industry has grown to
  18. ^ SecaaS Category 9 // BCDR Implementation Guidance CSA, retrieved 14 July 2014.
  19. ^ "Post-Disaster Recovery Planning Forum: How-To Guide, Prepared by Partnership for Disaster Resilience". University of Oregon's Community Service Center, (C) 2007, www.OregonShowcase.org. Retrieved October 29, 2018.
  20. ^ "The Importance of Disaster Recovery". Retrieved October 29, 2018.
  21. ^ "IT Disaster Recovery Plan". FEMA. 25 October 2012. Retrieved 11 May 2013.
  22. ^ The Professional Practices for Business Continuity Management, Disaster Recovery Institute International (DRI), 2017
  23. ^ Gregory, Peter. CISA Certified Information Systems Auditor All-in-One Exam Guide, 2009. ISBN 978-0-07-148755-9. Page 480.
  24. ^ "Five Mistakes That Can Kill a Disaster Recovery Plan". Dell.com. Archived from the original on 2013-01-16. Retrieved 2012-06-22.
  25. ^ Brandon, John (23 June 2011). "How to Use the Cloud as a Disaster Recovery Strategy". Inc. Retrieved 11 May 2013.
  26. ^ "Info and video about Cisco's solution". Datacentreknowledge. May 15, 2007. Archived from the original on 2008-05-19. Retrieved 2008-05-11.
  27. ^ "Technical specs of Sun's Blackbox". Archived from the original on 2008-05-13. Retrieved 2008-05-11.
  28. ^ And English Wiki article on Sun's modular datacentre
  29. ^ Kidger, Daniel. "Mobull Plug and Boot Datacenter". Bull. Archived from the original on 2010-11-19. Retrieved 2011-05-24.
  30. ^ "HP Performance Optimized Datacenter (POD) 20c and 40c - Product Overview". H18004.www1.hp.com. Retrieved 2013-08-30.
  31. ^ "FitMDC Modular Data Center Solution".
  32. ^ "Huawei's Container Data Center Solution". Huawei. Retrieved 2014-05-17.
  33. ^ Kraemer, Brian (June 11, 2008). "IBM's Project Big Green Takes Second Step". ChannelWeb. Archived from the original on 2008-06-11. Retrieved 2008-05-11.
  34. ^ "Modular/Container Data Centers Procurement Guide: Optimizing for Energy Efficiency and Quick Deployment" (PDF). Archived from the original (PDF) on 2013-05-31. Retrieved 2013-08-30.
  35. ^ Slessman, George (May 7, 2013), System and method of providing computer resources, retrieved 2016-02-24
  36. ^ "Modular Data Center Firm IO to Split Into Two Companies". Data Center Knowledge. Retrieved 2016-02-24.

Further reading[edit]

  • ISO/IEC 22301:2012 (replacement of BS-25999:2007) Societal Security – Business Continuity Management Systems – Requirements
  • ISO/IEC 27001:2013 (replacement of ISO/IEC 27001:2005 [formerly BS 7799-2:2002]) Information Security Management System
  • ISO/IEC 27002:2013 (replacement of ISO/IEC 27002:2005 [renumbered ISO17799:2005]) Information Security Management – Code of Practice
  • ISO/IEC 22399:2007 Guideline for incident preparedness and operational continuity management
  • ISO/IEC 24762:2008 Guidelines for information and communications technology disaster recovery services
  • The Professional Practices for Business Continuity Management, Disaster Recovery Institute International (DRI), 2017
  • IWA 5:2006 Emergency Preparedness—British Standards Institution –
  • BS 25999-1:2006 Business Continuity Management Part 1: Code of practice
  • BS 25999-2:2007 Business Continuity Management Part 2: Specification
  • BS 25777:2008 Information and communications technology continuity management – Code of practice—Others –
  • "A Guide to Business Continuity Planning" by James C. Barnes
  • "Business Continuity Planning", A Step-by-Step Guide with Planning Forms on CDROM by Kenneth L Fulmer
  • "Disaster Survival Planning: A Practical Guide for Businesses" by Judy Bell
  • ICE Data Management (In Case of Emergency) made simple – by MyriadOptima.com
  • Harney, J.(2004). Business continuity and disaster recovery: Back up or shut down.
  • AIIM E-Doc Magazine, 18(4), 42–48.
  • Dimattia, S. (November 15, 2001).Planning for Continuity. Library Journal,32–34.

External links[edit]