Algorithm¶

top-BDII availability/reliability statistics are based on availability/reliability data that is published by MyEGI through the SAM Programmatic Interface (SAM PI). MyEGI is the authoritative source of availability/reliability data

A brief description of the algorithm adopted to compute top-BDII availbility and reliability statistics follows.

Different schenarios are possible.

Scenario 1. Single top-BDII¶

The NGI reports only one Top-BDII. It could be a single top-bdii instance, or alternatively a DNS alias for a pool of top-BDII instances (the DNS alias MUST BE monitored by the NGI Nagios). In this case Availability and Reliability are the monthly Availability and Reliability reported directly by the MyEGI Programmatic Interface.

Note: If the alias is used by the sites but only the single instances in the pool are monitored by Nagios, then in the table above the list of instances per NGI has to be reported. In this case Availability and Reliability are computed according to Scenario 2.

Scenario 2. List of top-BDIIs¶

The NGI reports a list of top-BDIIs. These are all used by the sites to configure failover at client side. In this case the algorithm steps are the following:

Query MyEGI to get the hourly A/R values for every top-BDII instance in the list.

• Hourly Availability and Reliability: given the list of Availability/Reliability figures for the top-BDII in the list, the maximum
• Availability/Reliability figures are computed. These are selected to be the hourly Availability/Reliability.
• Monthly Availability and Reliability: the monthly Availability/Reliability is the arithmetic mean of the hourly Availability/Reliability figures in the reference month:

  Monthly A/R: (sum of the Hourly A/R figures)/(number of hours when the status was known).