HPP Enterprises P4000 SAN - Manual (Page 40)

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 Appropriate physical and virtual networks exist at both sites.
Alternatively, the multi-site SAN feature can be implemented by correct physical node placement of
single site cluster.
In a two-site implementation, you need an even number of storage nodes whether you have chosen a
single-site cluster or multi-site SAN. Each site must contain an equal number of storage nodes.
In the case of a single-site SAN that is physically separated, it is critical that either the order of nodes
in the cluster is appropriately created or the correct node is chosen from the order for physical
separation. This requirement is straightforward in a two-node cluster; however, with a four-node
cluster, you would deploy nodes 1 and 3 at Site A, while deploying nodes 2 and 4 at Site B. With
the four-node cluster, volumes must, at a minimum, be configured for Replication Level 2; thus, even if
Site A or B were to go down, storage nodes at the surviving site can still access the volumes required
to support local VMs as well as protected VMs from the failed site.
You can find the order of storage nodes in the CMC by editing the cluster, as shown in Figure 33. If
desired, you can change the order by highlighting a particular storage node and moving it up or
down the list. Note that changing the order causes all volumes in the cluster to be restriped, which
may take some time.
Figure 33. Editing the cluster