I guess today’s topic gets most business managers interested. Systems are never an issue until they stop running. So keeping them running is critical. This week we continue briefly with our discussion of disaster recovery and prevention, and then turn to high availability systems.
In many cases, an organisation may elect to use an outsourced disaster recovery provider to provide a stand-by site and systems rather than using their own remote facilities.
In addition to preparing for the need to recover systems, organisations must also implement precautionary measures with an objective of preventing a disaster in the first place. These may include some of the following:
Local mirrors of systems and/or data and use of disk protection technology such as RAID
Surge protectors — to minimise the effect of power surges on delicate electronic equipment
Uninterruptible power supply (UPS) and/or backup generator to keep systems going in the event of a power failure
Fire preventions — alarms, fire extinguishers
Anti-virus software and other security measures
Fortunately, as a Mac user I don’t need to worry about Anti-virus software. On Windows you will need the latest and the greatest to prevent attack.
But lets focus on high availability, and again I quote from Wikipedia:
“High availability is a system design approach and associated service implementation that ensures a prearranged level of operational performance will be met during a contractual measurement period.”
Users want their systems, for example wrist-watches, hospitals, airplanes or computers, to be ready to serve them at all times.
Availability refers to the ability of the user community to access the system, whether to submit new work, update or alter existing work, or collect the results of previous work. If a user cannot access the system, it is said to be unavailable. Generally, the term downtime is used to refer to periods when a system is unavailable.
A distinction can be made between scheduled and unscheduled downtime. Typically, scheduled downtime is a result of maintenance that is disruptive to system operation and usually cannot be avoided with a currently installed system design. Scheduled downtime events might include patches to system software that require a reboot or system configuration changes that only take effect upon a reboot.
In general, scheduled downtime is usually the result of some logical, management-initiated event. Unscheduled downtime events typically arise from some physical event, such as a hardware or software failure or environmental anomaly. Examples of unscheduled downtime events include power outages, failed CPU or RAM components (or possibly other failed hardware components), an over-temperature related shutdown, logically or physically severed network connections, catastrophic security breaches, or various application, middleware, and operating system failures.
Many computing sites exclude scheduled downtime from availability calculations, assuming, correctly or incorrectly, that scheduled downtime has little or no impact upon the computing user community. By excluding scheduled downtime, many systems can claim to have phenomenally high availability, which might give the illusion of continuous availability.”
We will continue to explore high availability systems next time, just note already that costs of availability are extremely high and increase exponentially with an increase in availability. Not only because multiple redundant systems are necessary but also because of higher staff costs to manage such systems. This is where SAAS has so many advantages.
But lets discuss this next time, and remember……keep it (A)FRESH!
Source:http://www.economist.com.na/index.php?option=com_content&view=article&id=22394:hard-facts-on-software-a-fresh-look-at-high-availability-systems&catid=570:columns&Itemid=66