Novell BUSINESS CONTINUITY CLUSTERING 1.2.1 - ADMINISTRATION, Руководство администратора, Страница: 15 / 184

Overview of Business Continuity Clustering 15
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Table 1-1 compares the benefits and limitations of host-based and storage-based mirroring.
Table 1-1
Comparison of Host-Based and Storage-Based Data Mirroring
1.2.3 Stretch Clusters vs. Cluster of Clusters
A stretch cluster and a cluster of clusters are two clustering implementations that you can use with
Novell Cluster Services
TM
to achieve your desired level of disaster recovery. This section describes
each deployment type, then compares the capabilities of each.
Novell Business Continuity Clustering automates some of the configuration and processes used in a
cluster of clusters. For information, see
Section 1.3, “Business Continuity Clustering,” on page 20 .
Š
“Stretch Clusters” on page 15
Š
“Cluster of Clusters” on page 16
Š
“Comparison of Stretch Clusters and Cluster of Clusters” on page 17
Š
“Evaluating Disaster Recovery Implementations for Clusters” on page 19
Stretch Clusters
A stretch cluster consists of a single cluster where the nodes are located in two geographically
separate data centers. All nodes in the cluster must be in the same Novell eDirectory
TM
tree, which
requires the eDirectory replica ring to span data centers. The IP addresses for nodes and cluster
resources in the cluster must share a common IP subnet.
Capability Host-Based Mirroring Storage-Based Mirroring
Geographic distance between
sites Up to 10 km Can be up to and over 300 km.
The actual distance is limited only
by the SAN hardware and media
interconnects for your
deployment.
Mirroring the SBD partition An SBD can be mirrored between
two sites. Yes, if mirroring is supported by
the SAN hardware and media
interconnects for your
deployment.
Synchronous data-block
replication of data between sites Yes Yes, requires a Fibre Channel
SAN or iSCSI SAN.
Failover support No additional configuration of the
hardware is required. Requires additional configuration
of the SAN hardware.
Failure of the site interconnect LUNs can become primary at
both locations (split brain
problem). Clusters continue to function
independently. Minimizes the
chance of LUNs at both locations
becoming primary (split brain
problem).
SMI-S compliance If the storage subsystems are not
SMI-S compliant, the storage
subsystems must be controllable
by scripts running on the nodes of
the cluster. If the storage subsystems are not
SMI-S compliant, the storage
subsystems must be controllable
by scripts running on the nodes of
the cluster.