North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: Quick Question on Industry Standard
Title: RE: Quick Question on Industry Standard -----Original Message-----
From my understanding there is a 99.97% up time value that most companies try
Cisco references that figure in their MTBF/MTTR (mean time before failure) calculations, however they also reference 99.9%. Our organization does not include scheduled maintenance in our HA (high availability) calculations, and I expect most organizations don't either. Quote, "Availability is calculated using statistical models for all the system components, the simplest model for a component being binary. The component is either in or out of service. Availability can be calculated from failure rates, measured in mean time between failures (MTBF), and repair times, measured in mean time to repair (MTTR)." Also, "The average downtime contribution by any component is calculated by amortizing the MTTR time over the MTBF period. For example, if a component critical to the operation of the platform has an MTBF of 250,000 hours and a MTTR of 1 hour, it contributes 2.1 minutes (60 min/250,000 hr/8760 hr/yr) of unavailability to the system per year" http://www.cisco.com/warp/public/cc/pd/rt/7500/prodlit/haibd_ov.htm So to calculate the physical HA stats, you need to reduce your network to component levels and do the calculations. Cables are not usually included in these calculations. HTH -- Tim
|