Hardware Availability Assessment - Avaya Application Solutions Deployment Manual

The data required for predicting system availability is limited to unplanned outage frequency
and downtime experienced by service interruption. Potential outages are defined as follows:
A Reportable Outage: "A reportable outage is an event that includes total loss of
origination and termination capability in all switch terminations for greater than 30 seconds
period (uninterrupted duration)."
Outage Downtime Measure: "An outage downtime Performance Measure is the
expected long-term average sum, over one operating year, of the time durations of events
that prevent a user from requesting or receiving services. A failure that causes service
interruption contributes to the outage downtime of that service. Outage downtime is
usually expressed in terms of minutes of outage per year."
Downtime Measure for Partial Outages: "The downtime measure for Partial Outage
Events is a Weighted Downtime Performance Measure. The actual time duration of a
partial outage is weighted by the fraction of switch terminations affected by the outage
condition."
The following criteria are also considered when assessing system availability:
* Only unplanned downtime will count against availability of the system/switch. For
example, if software upgrades require service interruption, the downtime associated with
firmware and software upgrades is considered to be "planned," and by definition, will not
count against the availability of the system.
* Outages of the enterprise's IP data network and failure of non-Avaya products will not
count against the availability score for the Avaya furnished solution components
(products).
* Downtime due to operator error will not count against system availability.

Hardware Availability Assessment

The hardware availability prediction follows the following steps
A. MTBF and FIT data
The MTBF (Mean Time Between Failure) and FIT (Failure in Time Rate) data of individual
components are estimated based on Telecordia recommended "Part Count Method". This
process consists of summing the failure rates of all devices comprising the module.
extended field performance data of the module is available, typically based upon a review of two
(2) years of marketplace performance in a variety of settings for numerous enterprises, a more
accurate MTBF can be estimated.
4 Telecordia (Bellcore) GR-512, Requirement R3-1, Hardware Reliability Modeling Methods, Section 3.1, Method
I of Reliability Prediction Procedure for Electronic Equipment (RPP).
Design for High Availability
4
When
Issue 3.4.1 June 2005 257