Logical unit numbers (LUNs) for fibre-channel ports

The SAN Volume Controller supports a maximum of 2048 LUNs per I/O group, with a maximum of 512 configured to any one host.

Each virtual disk that is created on the SAN Volume Controller can be mapped to multiple HBA fibre-channel ports in a given host. There can also be multiple paths across the SAN. For these reasons, each host must run multipathing software, such as the subsystem device driver (SDD). The multipathing software manages the many paths that are available to the virtual disk and presents a single storage device to the operating system. The SAN Volume Controller supports a variety of multipathing software. The specific multipathing software that is supported by the SAN Volume Controller depends on the host operating system with which it is being used.

• The number of paths through the network from the SAN Volume Controller nodes to a host must not exceed 8. Configurations in which this number is exceeded are unsupported.
  • Each SAN Volume Controller node has four ports and each I/O group has two SAN Volume Controller nodes. Therefore, without any zoning, the number of paths to a VDisk is 8 × the number of host ports.
  • This rule exists to limit the number of paths that must be resolved by the multipathing device driver.

If you want to restrict the number of paths to a host, zone the switches so that each HBA port is zoned with one SAN Volume Controller port for each node in the cluster. If a host has multiple HBA ports, zone each port to a different set of SAN Volume Controller ports to maximize performance and redundancy.