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 information technology (IT) or technology systems supporting critical business functions[1] as opposed to business continuity. This involves keeping all essential aspects of a business functioning despite significant disruptive events; it can therefore be considered a subset of business continuity.[2][3] Disaster recovery assumes that the primary site is not recoverable for some time and represents a process of restoring data and services to a secondary survived site, which is opposite to restoring it back to its original place.

IT service continuity[edit]

IT Service Continuity[4][5] (ITSC) is a subset of business continuity planning (BCP)[6] that focuses on Recovery Point Objective (RPO) and Recovery Time Objective (RTO). It encompasses two kinds of planning; IT disaster recovery planning and wider IT resilience planning. It also incorporates IT infrastructure and services related to communications, such as (voice) telephony and data communications.

Principles of backup sites[edit]

Planning includes arranging for backup sites, whether they are hot, warm, or cold, and 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 This was withdrawn following the publication in March 2011 of ISO/IEC 27031, "Security techniques — Guidelines for information and communication technology readiness for business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."[7]

ITIL has defined some of these terms.[8]

Recovery Time Objective[edit]

The Recovery Time Objective (RTO)[9][10] 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.[11]

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

Example showing longer 'actual' times that do NOT meet either RPO or RTOs ('objectives'). Diagram provides schematic representation of the terms RPO and RTO.

Literature on the subject refers to RTO as a complement of Recovery Point Objective (RPO), with two metrics describing the limits of acceptable or "tolerable" ITSC performance. RTO and RPO gauges ITSC performance in terms of time lost from normal business process functioning and data lost or not backed up during that period (RPO), respectively.[11][12]

Recovery Time Actual[edit]

A Forbes overview[9] noted Recovery Time Actual (RTA) is, in fact, the critical metric for business continuity and disaster recovery.

The business continuity group conducts timed rehearsals (or actuals), during which RTA gets determined and refined as needed.[9][13]

Recovery Point Objective[edit]

A Recovery Point Objective (RPO) is the maximum targeted period during which transactional data is lost from an IT service due to a major incident.[11]

For example, in the case, RPO is measured in minutes (or even a few hours), then in practice, off-site mirrored backups must be continuously maintained as a daily off-site backup on tape will not suffice.[14]

Relationship to Recovery Time Objective[edit]

A recovery that is not instantaneous will restore transactional data over some time and do so without incurring significant risks or losses.[11]

RPO measures the maximum time in which recent data might have been permanently lost in the event of a major incident and is not a direct measure of the quantity of such loss. For instance, if the BC plan, to restore up to the last available backup, then the RPO is the maximum interval between such backups that have been safely vaulted off-site.

It is often misinterpreted that RPO is determined by the existing backup regime, whereas in reality, Business impact analysis determines RPO for each service. When off-site data is required, the period during which data might be lost often starts when backups are prepared, not when the backups are taken off-site.[12]

Data synchronization points[edit]

A data synchronization point[15] is a point in time when physical data is backed up. It is one of the approaches used to halt the processing of an update queue, while a disk-to-disk copy is being made. The backup[16] copy would reflect the earlier version of the 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, taking business risk into account, along with all the other major system design criteria.[17]

RPO is tied to the times' backups are sent offsite. Offsiting via synchronous copies to an offsite mirror allows for most unforeseen difficulty. The 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 complete the package needed.[18]

For high volumes of high-value transaction data, the hardware can be split across two or more sites by 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[19][20] developed to provide backup computer centers. One of the earliest such centers was located in Sri Lanka (Sungard Availability Services, 1978).[21][22]

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.[23]

Classification of disasters[edit]

Disasters can be the result of three broad categories of threats and hazards. The first category is natural hazards that include acts of nature such as floods, hurricanes, tornadoes, earthquakes, and epidemics. The second category is technological hazards that include accidents or the failures of systems and structures such as pipeline explosions, transportation accidents, utility disruptions, dam failures, and accidental hazardous material releases. The third category is human-caused threats that include intentional acts such as active assailant attacks, chemical or biological attacks, cyber attacks against data or infrastructure, and sabotage. Preparedness measures for all categories and types of disasters fall into the five mission areas of prevention, protection, mitigation, response, and recovery.[24]

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.[25]

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.[26]

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.[citation needed] 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.[27]

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 a 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.[28] 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 and Recovery Time Objective.[29] Metrics for business processes are then mapped to their systems and infrastructure.[30]

Failure to properly plan can extend the disaster's impact.[31] Once metrics have been mapped, the organization reviews the IT budget; RTO and RPO metrics must fit with the available budget. A cost-benefit analysis often dictates which disaster recovery measures are implemented.

Adding cloud-based backup to the benefits of local and offsite tape archiving, the New York Times wrote, "adds a layer of data protection."[32]

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 a 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)[33]

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

Disaster recovery as a service[edit]

Disaster recovery as a service (DRaaS) is an arrangement with a third party, a vendor.[34] Commonly offered by Service Providers as part of their service portfolio.

Although vendor lists have been published, disaster recovery is not a product, it's a service, even though several large hardware vendors have developed mobile/modular offerings that can be installed and made operational in very short time.[35][original research?]

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. ^ "ISO 22301 to be published Mid May - BS 25999-2 to be withdrawn". Business Continuity Forum. 2012-05-03. Retrieved 2021-11-20.
  8. ^ "ITIL glossary and abbreviations".
  9. ^ a b c "Like The NFL Draft, Is The Clock The Enemy Of Your Recovery Time". Forbes. April 30, 2015.
  10. ^ "Three Reasons You Can't Meet Your Disaster Recovery Time". Forbes. October 10, 2013.
  11. ^ a b c d "Understanding RPO and RTO". DRUVA. 2008. Retrieved February 13, 2013.
  12. ^ a b "How to fit RPO and RTO into your backup and recovery plans". SearchStorage. Retrieved 2019-05-20.
  13. ^ "Clock... modifications
  14. ^ Richard May. "Finding RPO and RTO". Archived from the original on 2016-03-03.
  15. ^ "Data transfer and synchronization between mobile systems". May 14, 2013.
  16. ^ "Amendment #5 to S-1". SEC.gov. real-time ... provide redundancy and back-up to ...
  17. ^ Peter H. Gregory (2011-03-03). "Setting the Maximum Tolerable Downtime -- setting recovery objectives". IT Disaster Recovery Planning For Dummies. Wiley. pp. 19–22. ISBN 978-1118050637.
  18. ^ William Caelli; Denis Longley (1989). Information Security for Managers. p. 177. ISBN 1349101370.
  19. ^ "Catastrophe? It Can't Possibly Happen Here". The New York Times. January 29, 1995. .. patient records
  20. ^ "Commercial Property/Disaster Recovery". NYTimes.com. October 9, 1994. ...the disaster-recovery industry has grown to
  21. ^ Charlie Taylor (June 30, 2015). "US tech firm Sungard announces 50 jobs for Dublin". The Irish Times. Sungard .. founded 1978
  22. ^ Cassandra Mascarenhas (November 12, 2010). "SunGard to be a vital presence in the banking industry". Wijeya Newspapers Ltd. SunGard ... Sri Lanka's future.
  23. ^ SecaaS Category 9 // BCDR Implementation Guidance CSA, retrieved 14 July 2014.
  24. ^ "Threat and Hazard Identification and Risk Assessment (THIRA) and Stakeholder Preparedness Review (SPR): Guide Comprehensive Preparedness Guide (CPG) 201, 3rd Edition" (PDF). US Department of Homeland Security. May 2018.
  25. ^ "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.
  26. ^ "The Importance of Disaster Recovery". Retrieved October 29, 2018.
  27. ^ "IT Disaster Recovery Plan". FEMA. 25 October 2012. Retrieved 11 May 2013.
  28. ^ "Cloud Disaster Recovery: well-prepared for worst case scenario". IONOS Digitalguide. Retrieved 2022-06-23.
  29. ^ "Use of the Professional Practices framework to develop,implement,maintain a business continuity program can reduce the likelihood of significant gaps". DRI International. 2021-08-16. Retrieved 2021-09-02.
  30. ^ Gregory, Peter. CISA Certified Information Systems Auditor All-in-One Exam Guide, 2009. ISBN 978-0-07-148755-9. Page 480.
  31. ^ "Five Mistakes That Can Kill a Disaster Recovery Plan". Dell.com. Archived from the original on 2013-01-16. Retrieved 2012-06-22.
  32. ^ J. D. Biersdorfer (April 5, 2018). "Monitoring the Health of a Backup Drive". The New York Times.
  33. ^ Brandon, John (23 June 2011). "How to Use the Cloud as a Disaster Recovery Strategy". Inc. Retrieved 11 May 2013.
  34. ^ "Disaster Recovery as a Service (DRaaS)".
  35. ^ "Cloud backup and recovery".
  36. ^ "Info and video about Cisco's solution". Datacentreknowledge. May 15, 2007. Archived from the original on 2008-05-19. Retrieved 2008-05-11.
  37. ^ 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.
  38. ^ "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.
  39. ^ Kidger, Daniel. "Mobull Plug and Boot Datacenter". Bull. Archived from the original on 2010-11-19. Retrieved 2011-05-24.
  40. ^ "HP Performance Optimized Datacenter (POD) 20c and 40c - Product Overview". H18004.www1.hp.com. Archived from the original on 2015-01-22. Retrieved 2013-08-30.
  41. ^ "Huawei's Container Data Center Solution". Huawei. Retrieved 2014-05-17.
  42. ^ "Technical specs of Sun's Blackbox". Archived from the original on 2008-05-13. Retrieved 2008-05-11.

Further reading[edit]

External links[edit]