IBM N Series - HA Pair Types and Requirements; Standard HA Pairs

76 IBM System Storage N series Hardware Guide
򐂰 iSCSI network-attached topologies are topologies in which the hosts are attached to
storage controllers through Ethernet switches. Networks can contain multiple Ethernet
switches in any configuration.
򐂰
Mirrored HA pair configuration is similar to the standard HA pair configuration, except
that there are two copies, or
plexes, of the data. This configuration is also called data
mirroring
.
򐂰
Remote storage refers to the storage that is accessible to the local node, but is at the
location of the remote node.
򐂰
Single storage controller configurations are topologies in which there is only one storage
controller is used. Single storage controller configurations have a single point of failure and
do not support cfmodes in Fibre Channel SAN configurations.
򐂰
Standard HA pair configuration refers to a configuration set up in which one node
automatically takes over for its partner when the partner node becomes impaired.
7.2 HA pair types and requirements
The following types of HA pairs are available, each having distinct advantages and
requirements:
򐂰 Standard HA pairs
򐂰 Mirrored HA pairs
򐂰 Stretch MetroClusters
򐂰 Fabric-attached MetroClusters
Each of these HA pair types is described in the following sections.
7.2.1 Standard HA pairs
In a standard HA pair, Data ONTAP functions so that each node monitors the functioning of its
partner through a heartbeat signal that is sent between the nodes. Data from the NVRAM of
one node is mirrored by its partner. Each node can take over the partner’s disks or array
LUNs if the partner fails. Also, the nodes synchronize time.
Standard HA pairs have the following characteristics:
򐂰 Standard HA pairs provide high availability by pairing two controllers so that one can serve
data for the other in case of controller failure or other unexpected events.
򐂰 Data ONTAP functions so that each node monitors the functioning of its partner through a
heartbeat signal that is sent between the nodes.
򐂰 Data from the NVRAM of one node is mirrored by its partner. Each node can take over the
partner’s disks or array LUNs if the partner fails.
Tip: You must follow certain requirements and restrictions when you are setting up a new
HA pair configuration. These restrictions are described in the following sections.