ISL over Subscription Ratio
SAN Fan–in and Fan-Out
Storage Ports
Server I/O Profiles
Fabric Features
Continuity Requirements
Design should address three separate levels:
Tier 1: 99.999% availability (5 minutes of downtime per year)
Tier 2: 99.9% availability (8.8 hours average downtime per year, 13.1 hours maximum)
Tier 3: 99% availability (3.7 days of downtime per year)
