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Do you trust your backups? Read More

Conclusion

Business Continuity of a company are defined according to RTO and RPO. An availability strategy of an information service should be defined according to the following 4 time segments:

Conclusion

  • From T ­­ 0to T ­­ 1: this time interval is between the time the incident occurs and the time we have the latest copy of the backed-up data. This interval thus corresponds to the RPO.
  • From T ­ 1to T ­­ 2: this time interval starts from the moment the incident occurs and ends when the recovery process is completed. This process is activated by an operator or control software. There is a service unavailability during this period of time.
  • From T ­­ 2to T ­­ 3: this time interval determines the time of operations in degraded mode of the system. It matches to the time required to cope with a new incident leading to a service interruption.
  • From T ­­ 3to T ­­ 4: this time interval determines the time required to return to normal production, without degradation of service or performance.

Clustering

This technology aims to increase the availability of applications which are critical and compatible with this one. The principle is to immediately have a second server in case of failure of the first one. There is an automatic switching over of the application to a redundant or standy server (Failover) through a process of mutual verification of proper operation if any component of the software or hardware supported and supervised by the clustering software were to fail. This mechanism allows to reduce or to make completely invisible to users a major failure of one of the systems. The level of availability is thus significantly increase. Once the component is replaced and the server is back in production, the restoration of a failed system component's share of a load to a replacement component after a failback event (failback) can be executed at administrator's request. We distinguish clustering solutions in "active-passive" or "active-active" mode. In the first case, one of the servers (or node) is standby and ready to support the application executed on the active node. In the other mode, both nodes or n -nodes are simultaneously active and share the application workloads. The level of availability is highter than an active-passive solution, however the cost and complexity of such a solution are much higher. It is also possible to implement extended clustering solution (stretched cluster). In this case, the cluster nodes are on geographically remote sites. Such a complex and onerous solution is for applications requiring very high availability of service.

Read More... Virtualization

Business Continuity

Business Continuity should be in compliance with the following three points:

  • available on demand and at any time
  • with acceptable performances in response to requests in difficult circumstances
  • with acceptable features in response to requests in difficult circumstances
Computer technologies such as "high availability" solutions allow a system to perform without disruption during a period of time superior to that guaranteed by each of its component. High availability is often achieved through a breakdown tolerance.

The information system architect should:

  • define what availability means in the context of the information system
  • combine the appropriate hardware and software to create a highly available information system


It has been designed to find answers to the following questions:

  • how long should the system be available? At what frequency is it used?
  • what are the consequences if the system is unavailable when it is required?
Read More... Types of breakdown

Degraded Operation Interval

Time between the component failure and its replacement to ensure redundancy. A second failure similar the second one during this period thus leads to a service interruption which can be longer than the previous one if restoration then becomes impossible.

Degraded Operation Interval

Planned Downtime : time to be planned so as to proceed to full restoration following failure or a disaster.

Lire la suite... Conclusion