IBM N Series, Hardware Manual

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IBM System Storage N series Hardware Guide
8.3.1 Planning Stretch MetroCluster configurations
For planning and sizing Stretch MetroCluster environments, remember the following
considerations:
򐂰 Use multipath HA (MPHA) cabling.
򐂰 Use FibreBridges with SAS Shelves (EXN3000 & EXN3500).
򐂰 N62x0 and N7950T systems require FC/VI cards for Fabric MetroClusters.
򐂰
Provide enough ports or loops to satisfy performance (plan for more adapters if
appropriate).
Stretch MetroCluster controllers connect directly to local shelves and remote shelves. The
minimum is four FC ports per controller for a single stack (or loop) configuration. However,
you mix the pools of the different two controllers in each stack, as shown in Figure 8-4.
Figure 8-4 Stretch MetroCluster setup with only one stack per site
Because of the SyncMirror feature and the mirrored plexes (pool0 and pool1), disk failures
have no operational impact. All disks, including spare disks, must be manually assigned to
each pool.
MetroCluster design features the following important considerations:
򐂰 Stretch MetroCluster has no imposed spindle limits, only the platform limit.
򐂰 Take care in planning N6210 MetroCluster configurations because the N6210 has only two
FC initiator onboard ports and two PCI expansion slots. Because you use one slot for the
FC/VI adapter, you have only one remaining slot for an FC initiator card. Because you
need four FC ports, which are needed for Stretch MetroCluster, the following
configurations are possible:
– Two onboard FC ports + dual port FC initiator adapter
– Quad port FC initiator HBA (frees up onboard FC ports)
All slots are used and the N6210 cannot be upgraded with other adapters.
Requirement: A Stretch MetroCluster solution requires at least four disk shelves.