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High Availability Requirements

Number of impacted users and the impact severity
Number of impacted external customers and the impact severity
Number of other services affected and the impact severity
Availability requirements are defined based on:
Available budget

Service Level Agreements

An SLA includes:
Requirements for availability
Recovery times and processes
Penalties for non-compliance
Escalation procedures
• SLAs can be formal or informal

Components of a High Availability Design

A high availability design must include:
– Backup and recovery design
– High availability of services design
Infrastructure Requirements for High Availability
High availability requires that infrastructure is highly available, including:
Physical infrastructure such as power supplies and cooling
Server hardware
Network hardware
Active Directory Domain Services
DNS
Considerations for Storing Application Data for  NLB
– All servers must have the same data
– Data can be stored in a central location
– Data can be synchronized between servers
• The suitability of an application for NLB depends on how data is stored

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