A SAN Volume Controller cluster
that uses SAN fabric switches can connect to application hosts, storage
controllers, or other SAN Volume Controller clusters
through the use of short- or long-wave optical fiber connections.
The
maximum distance between the cluster and host
or the cluster and the storage controller is 300 m for short-wave
optical connections and 10 km for long-wave optical connections. Longer
distances are supported between clusters that use the intercluster
Metro Mirror or Global Mirror feature.
When you
use long-wave optical fiber connections,
follow these guidelines:
- For disaster recovery,
each cluster must be regarded
as a single entity. This includes the back-end storage that provides
the quorum disks for the cluster. Therefore, the cluster and quorum
disks must be co-located.
- The maximum permitted
distance
between nodes within a cluster is 100 meters. There can be a large
fibre-cable distance between the same nodes in the cluster; however,
the nodes must be physically co-located to permit effective service
and maintenance. For example, the nodes could be 300 meters away for
2Gbs connections or 150 meters away for 4Gbs connections from the
SAN fabric for a maximum total of 600 meters cable distance between
the nodes; however, the nodes must be physically within 100 meters
of each other.
- All nodes in a cluster
must be on the same IP subnet. This allows
the nodes to assume the same cluster or service IP address.
- A
node must be on the same rack as the uninterruptible
power supply from
which it receives power.
Note: Do not split cluster
operation over a long optical
distance; otherwise, you will only be able to use asymmetric disaster
recovery and it will have substantially reduced performance. Instead,
use two cluster configurations for all production disaster recovery
systems.