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Table 3 Common Multi-Site SAN configurations with recommended managers
Number of managers and number
Needed to maintain quorum
Manager configurationMulti-Site SAN configuration
• Manager count = three
Number for quorum = two
• Manager count = five
Number for quorum = three
For four storage systems, run:Two physical sites, one site is primary
• Two managers in the primary site
• One manager in the secondary site
For six storage systems or more, run:
• Three managers in the primary site
• Two managers in the secondary site
• Manager count = three
Number for quorum = two
• Manager count = five
Number for quorum = three
For two storage systems, run:Two physical sites, logical third site
• One manager in each site
• One failover manager in the logical
third site
• Two managers in each site, one
failover manager in the logical third
site
For four storage systems or more, run:
• Two managers in each site
• One failover manager in the logical
third site
For two storage systems, run:Three physical sites, cluster spans two
sites
• Manager count = three
Number for quorum = two
• One manager in each site
• One failover manager in the third
site
• Manager count = five
Number for quorum = three
For four storage systems, run:
• Two managers in each site
• One failover manager in the third
site
For three storage systems, run:
• One manager in each site
For six or more storage systems, run:
Three physical sites
• Manager count = three
Number for quorum = two
• Manager count = five
Number for quorum = three
• Three managers in the primary site
• Two managers in the secondary site
Configuring data replication for optimal availability and redundancy
The LeftHand OS software offers six levels of synchronous replication at a volume level. However,
only three levels are appropriate for Multi-Site SAN configurations. Table 4 (page 17) describes
the appropriate data replication levels for the Multi-Site SAN and associated supported
configurations. To protect the data across sites, you must choose a data protection level with a
number of mirrors that is at least equal to the number of sites in the configuration. For example, if
the storage cluster spans three sites, then volumes must be configured as Network RAID–10+1 in
order to ensure that data is the same on each site.
NOTE: Network RAID-0, Network RAID-5, and Network RAID-6 do not tolerate site failures.
16 Designing a Multi-Site SAN