Database Reference
In-Depth Information
Flex ASM and Flex Clusters
In Flex Clusters, Leaf nodes are not required to have direct storage access. In order for applications' Leaf nodes to
access ASM disks on the shared storage through the Hub nodes, Oracle Flex ASM is required in Oracle Flex Clusters.
If you configure an Oracle Flex Cluster during the Oracle GI installation OUI, the Oracle Flex ASM is enabled by
default and the Flex ASM will be configured as a part of the GI installation. If you convert a standard cluster to a Flex
Cluster after the OUI installation, you need to enable the Flex ASM on the cluster before changing the cluster mode to
the Flex Cluster.
In a Flex Cluster configuration, ASM instances have to run the Hub nodes because Hub nodes are required
to have direct access the shared storage. However, not all Hub nodes may run Oracle ASM instances. As shown in
Figure
4-5
, by default only three Hub nodes run Oracle ASM instances and other Hub nodes, such as node 4, run Flex
ASM client without ASM instances on it. Therefore, in a Flex Cluster only a subset of the Hub nodes hosts the Flex
ASM I/O service.
Oracle Flex ASM also can run on a standard cluster mode. In this case, all the cluster nodes are Hub nodes and
only a subset of the standard cluster nodes run ASM instances.
Configuring Flex ASM
Oracle Flex ASM can be configured during the GI installation with OUI or can be converted from a standard ASM after
the installation.
During the GI installation, as we mentioned previously, if you select the Flex Cluster option, the Flex ASM
is automatically selected by default. If you select the standard Cluster option, you will have options to select the
standard ASM or the Flex ASM. As long as the Flex ASM option is selected either by default or manually, as part of the
GI installation, you will need to configure the ASM network by providing at least one physical network interface for the
ASM network. In Oracle 12cR1, you can either have a separate network for the ASM network or have the ASM network
and Private interconnects sharing the same physical network interfaces. Figure
4-7
shows a configuration where the
ASM network and the Private interconnect share both eth1 and eth2 network interfaces.
Figure 4-7.
ASM network and private interconnects share the same physical NICs
The Flex ASM configuration is completed as a part of the GI installation process. By default, three-node Hub
nodes will be chosen to run the ASM instances and the rest of the cluster nodes will be Flex ASM clients. The Flex ASM
listener will also be created.
You also can enable the Flex ASM on a standard ASM cluster by converting the standard ASM to the Flex ASM.
However, as the prerequisite, prior to the conversion, you need to have at least one network interface for the ASM
network.
