r20 - 2015-04-21 - 07:20:57 - StevenBeardYou are here: TWiki >  Deployment Web > DeploymentPlanningAndDesign > DisasterRecovery

Disaster recovery principles

Authors: StevenBeard, DanToczala, RalphSchoon
Build basis: None

High availability (HA) and disaster recovery (DR) are both related aspects of Wikipedia: Business continuity planning.

Disaster recovery is the process, policies and procedures related to preparing for recovery or continuation of technology infrastructure critical to an organization after a natural or human-induced disaster - Wikipedia: Disaster recovery.

This topic focuses upon a major failure of the primary data center requiring failover to a secondary disaster recover data center or fundamental rebuild of the primary data center.

The related High availability principles focuses on failure scenarios and recovery within the primary data center.

This topic outlines the different principles of DR that you should consider when designing a Rational development environment. It is critical that DR is considered from the outset of designing your environment because the design itself will constrain the DR solution. DR that is developed as an afterthought may result in significant rework of the environment or result in a suboptimal solution. However, the first thing to consider is what are your organizations real requirements for DR based on your business and technical needs and requirements for the environment itself.

Recovery point objective (RPO)

RPO (measure in time) is the maximum tolerable period of data, information and/or development effort etc. that can be lost from an environment due to a DR failure. An RPO of 1 hour means that an organization can always revert back to a restore point that is never more than one hour old. This would require that the organization executes backups or equivalent DR solutions every hour. Practically, a development environment may have a RPO of one day, which may mean that data is backed up every night at a specific time. Some organizations have a requirement that their development environment has an RPO less than 24 hours, which will usually require advanced approaches to back-up online.

Recovery time objective (RTO)

RTO (measured in time) is the measure of how long it takes an organization to restore services through either HA, DR, or any combination. An RTO of 15 minutes means that an organization can restore its environment within 15 minutes or less. Practically, most development environments measure their RTO in hours. As surprising as it may seem, some organizations measure RTO in days.

DR quality-of-service

Most organizations typically consider four different DR quality-of-service (QoS) levels for their enterprise:

  • Platinum: RPO = seconds, RTO = under two hours. Delivered by a Tier 7 infrastructure like GDPS.
  • Gold: RPO = two hours, RTO = six hours. Delivered by a Tier 4/5 database log mirror/log apply solution.
  • Silver: RPO = 24 hours, RTO = 48 hours. Delivered by a RPiT backup capability using a Tier 1-3 approach.
  • Bronze: RPO = 24 hours, RTO = 48 hours. Delivered by nightly backups for the purpose of DR using a Tier 1-3 approach.

Most development environments require bronze or silver disaster recover QoS. If the operational systems the development environment supports are business critical and may require timely development changes, a gold QoS maybe required. Only a very few development environment that support nationally critical operational systems, or massive national or international banking systems will ever require platinum QoS.

The primary question you should ask is: "How long can my operational systems go without being able to make a critical development change?" Further, does this require the whole development environment or just part?

Secondary questions that might contribute to deciding the QoS level require include:

  • How much in lost productivity does it cost your organization to have the development environment down per hour/day?
  • What are the implications of loosing some of you development data depending upon the RPO of your QoS level (quality and/or compliance)?
  • Would a limited development environment allow you to make critical development changes for operational systems, while you recover the development environment more slowly?
  • What is the balance between the cost of your DR solution and the resultant cost due to different QoS levels?

DR process and procedures

The following phases are the phases of any DR process. This section outlines the high-level steps needed for proper DR. A separate step-by-step DR document should be made available so administrators who are unfamiliar with Jazz can also perform these operations. The last subsection highlights the need to exercise these processes on a regular basis to ensure that DR processes and procedures provide adequate mitigation of the risks associated with loss of the Jazz systems and their data.

Some good examples of DR capabilities and processes can be seen in the Jazz Team Server Backup Details and the RRC Backup and Restore documents on the Jazz wiki site.

Notification/activation phase

During this phase, the Jazz administrator becomes aware of a loss of service. In some scenarios, this is detected electronically, and automated processes are kicked off. In other scenarios, the notification is more manual in nature.

After the Jazz administrator is aware of a potential loss of service, other impacted parties need to be notified immediately. At this point, the Jazz administrator and a other stakeholders will need to assess and identify the problem, and the correct DR procedures need to be identified and executed.

  • Notification procedures

  • Damage assessment

  • Plan activation

Recovery phase

During this phase, recovery assets are put into place and the DR procedures are completed. Recovery refers to the recovery of service for the end users and stakeholders of the Jazz infrastructure.

  • Sequence of recovery activities

  • Recovery procedures

Reconstitution phase

After service--possibly at a reduced performance or capacity--has been restored, the original issue must be addressed. After the cause of the loss of service has been identified and addressed, plans for moving back to the original production systems must be made and executed. This resumption of normal operations should occur with as little impact as possible to the Jazz user community.

  • Primary site recovery

  • Primary site replacement

Quarterly recovery drills

Several staff members should be trained and practiced in DR procedures. A regular DR drill enforces the training and verifies that the infrastructure and procedures are working and up-to-date.

The process to back up the repositories requires that the Jazz server be shut down in order to ensure that database integrity is maintained. Full backups, as opposed to incremental backups, should be performed, in order to ensure database integrity. After the backup is completed, the Jazz server processes can be restarted.

Related topics: Back up the Rational solution for Collaborative Lifecycle Management, High availability principles, Approaches to implementing high availability and disaster recovery for Rational Jazz environments

External links:

Additional contributors: None

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