availability solutions

availability solutions：

 

• Redundant hardware ready for “hot swapping” keeps information highly
available by having multiple copies of information (mirroring) or enough
extra information available to reconstruct information in case of partial loss
(parity, error correction). Hot swapping allows the administrator to replace
the failed component while the system continues to run and information
remains available; usually degraded performance results, but unplanned
downtime is avoided.
• Fault-tolerant technologies keep information available against not only
individual storage device faults but even against whole system failures. Fault
tolerance is among the most expensive possible solutions, and is justified
only for the most mission-critical information. All technology will eventually
experience a failure of some form. A company that would suffer irreparable
harm from any unplanned downtime, or which would accumulate millions
of dollars in losses for even a very brief unplanned downtime, can justify
paying the high cost for fault-tolerant systems.
• Service level agreements (SLAs) help service providers, whether they are
an internal IT operation or an outsourcer, decide what type of availability
technology is appropriate. From this determination, the price of a service orthe budget of the IT operation can be set. The process of developing an SLA
with a business is also beneficial to the business. While some businesses have
performed this type of introspection on their own, many have not, and being
forced to go through the exercise as part of budgeting for their internal IT
operations or external sourcing helps the business understand the real value
of its information.
• Solid operational procedures are also required to maintain availability.
The most reliable hardware with the highest redundancy or fault tolerance,
designed for the fastest mean time to repair, will mostly be a waste of money
if operational procedures, training, and continuous improvement are not part
of the operational environment: one slip of the finger by an IT administrator
can halt the most reliable system.

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