InfraOpt® GmbH - numerical evaluation, analysis, and certification of infrastructures, especially for data centres.

• 1. creation of the resilience diagram.

• 2. boolean modelling

• 3. data preparation

• 4. numerical analysis

• 5. targeted optimisations

However, the optimal data centre is always dependent on the specific requirements, taking into account the given possibilities.

The European EN 50600 series of standards and their international counterparts ISO/IEC 22237 and ISO/IEC 30134 play a central role here.

• Standards describe the recognised rules of technology.

• They cover the relevant areas over the data centre life cycle.

• There is the possibility of third-party certification.

In data centre practice, it is helpful to have standardised definitions of SLAs. Compliance can be measured using meaningful key performance indicators (KPIs) that quantify the different aspects of resilience.

Through the German Commission for Electrical Engineering („Deutsche Kommission für Elektrotechnik“ (DKE)), a working group has been set up, dedicated to the KPI for resilience. The following topics are introduced as an international standardisation proposal ISO/IEC TS 22237-31:

• Definition of SLA using attributes of resilience.

• KPI for different aspects of resilience

• Calculation methodologies for the application of the KPI

Definition of the SLA >> Validation of the design >> Validation of planning >> Monitoring of operation

The first step in the resilience analysis is the creation of the resilience diagram. Developed by subject matter experts, it includes the following details:

• All relevant subsystems of the infrastructure

• All functional links between the subsystems

• References to the components that make up the subsystems

• Definition of the operation point (OP)

• Availability class according to EN 50600-1 or ISO/IEC 22237-1

• Reporting period in years

• Maximum number of service violations allowed

• in the reporting period

• Maximum permissible period of unavailability

• in the reporting period

• Maximum number of 1-point faults (SPoF)

• of the infrastructure

• Availability calculated on the infrastructure model

Analysts transform the resilience diagram into the simulation software InfraOpt64. The subsystems receive data and properties so that a model of the infrastructure under investigation is created.

On this infrastructure model, SLAs can be validated as well as targeted optimisations of resilience aspects can be carried out by:

• Calculating reliability

• Calculation of inherent and operational availability

• Calculation of 1- and 2-fault tolerance

• Calculation of the reduced availability in the 1- and 2-fault case

• Blackout simulation

• Design variations with different redundancies

• Analyses with reduced load

• Comparison of different subsystems

• Importance analyses

• ... and much more

Inherent availability is a KPI for the probability that the infrastructure will function as expected under ideal operating and maintenance conditions.

It does not take into account times for repair initiation, spare parts procurement or logistics.

As an aspect of resilience, Inherent Availability has the following practical significance:

• Application in the design or planning phases

• Comparison of variants

• Determination of redundancies

• Dependent on the metrics MTBF and MTTR

Operational availability is a KPI for the probability that the infrastructure will function as expected under the given operating and maintenance conditions.

Planned and unplanned events as well as required times for logistics are taken into account.

As an aspect of resilience, Operational Availability has the following practical significance:

• Sensitive to infrastructure optimisation

• Basis for maintenance and repair plans

• Usable for logistics planning and material stockpiling

• Dependent on the metrics MTBM and MDT

Reliability is KPI for the probability that the infrastructure will function without error, within a given period of time, under acceptable operating conditions.

As an aspect of resilience, reliability has the following practical significance:

• Sensitivity to infrastructure optimisation

• Determination of redundancies

• Predictive repair or replacement

• Dependent on MTBF and operating time

Fault tolerance of an infrastructure refers to the ability of one or more subsystems to continue to function as intended in the event of a failure.

Single Point of Failure (SPoF) refers to a subsystem whose failure results in the infrastructure no longer functioning as intended.

Double Point of Failure (DPoF) refers to two subsystems whose simultaneous failure means that the function of the infrastructure is no longer given.

It is initially irrelevant whether the cause of failures are failures or maintenance measures.

The ability to absorb errors or to quickly return to the nominal state after errors are aspects of resilience.

The KPI of fault tolerance, measured as the number of SPoF and DPoF, are subject to optimisation.