9.5.01 HP P4000 SAN Solution User Guide (AX696-96168, February 2012)

10 Working with clusters
Clusters are groups of storage systems created in a management group. Clusters create a pool of
storage from which to create volumes. The volumes seamlessly span the storage systems in the
cluster. Expand the capacity of the storage pool by adding storage systems to the cluster.
Prerequisites
• An existing management group
• At least one storage system in the management group that is not already in a cluster
• A designated VIP address for the cluster
VIPs are required for iSCSI load balancing and fault tolerance, and for using HP DSM for MPIO.
For more information, see “iSCSI and the HP P4000 SAN Solution” (page 230).
Clusters and storage systems
When creating clusters and when adding storage systems to clusters, consider storage system
capacity and the number of storage systems planned.
• Storage system capacity—Typically you create clusters with storage systems of the same
capacity. While clusters can contain storage systems with different capacities, all storage
systems in a cluster operate at a capacity equal to that of the smallest-capacity storage system.
The capacity limitation applies to the available capacity as determined by the disk RAID level,
not the raw disk capacity. While you can mix storage systems with different RAID levels in a
cluster, the capacity will be determined by the mix of RAID levels.
This capacity impact is particularly important to consider when planning to add additional
storage systems to an existing cluster. If you add a storage system with a smaller capacity,
the capacity of the entire cluster will be reduced. For example, If you have three storage
systems, two of which have a RAID-determined capacity of 1 TB, and one of which has a
RAID-determined capacity of 2 TB, all three storage systems operate at the 1 TB capacity.
• Number of storage systems in clusters—The optimum number of storage systems in a cluster
ranges up to 10. For more information about the recommended maximum number of storage
systems that can be added safely to a cluster, see “Configuration Summary overview” (page 109)
or “Working with management groups” (page 104).
Creating a cluster
Creating a management group using the Management Group, Clusters, and Volumes wizard
creates the first cluster in that management group. Use the following steps to create additional
clusters in existing management groups.
1. Log in to the management group in which to create a cluster.
2. Right-click the storage system, and select Add to New Cluster.
3. Select New Cluster→Standard Cluster, and click Next.
4. Enter a meaningful name for the cluster.
A cluster name is case sensitive and must be from 1 to 127 characters.
5. Select one or more storage systems from the list to include in the cluster, and click Next.
6. Click Add in the Assign Virtual IPs and Subnet Masks window to add the VIP for the new
cluster.
7. Enter the VIP and the Subnet Mask and click OK, and then click Next.
8. (Optional) Enter information for creating the first volume in the cluster, or select Skip Volume
Creation.
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