PRIMECLUSTER Global File Services Configuration and Administration Guide 4.1 (Linux)

4.2.2 Node layout

In the GFS Shared File System, up to four nodes can share one file system simultaneously. Therefore, file system processing can continue even if the node (on which MDS manages file system meta-data) fails. For such operation, you must select two or more nodes on which MDS can operate and set these nodes as MDS nodes. From the MDS nodes, select the primary MDS node (on which the primary MDS usually operates), the secondary MDS node (on which the secondary MDS usually operates), and all nodes as standby MDS nodes (backup MDS nodes if primary and secondary MDS nodes are unavailable).

For details on the effects of MDS node settings, see "MDS Failure Recovery."

As previously described in "Effects of file system operation and system load," the following should be taken into consideration:

• CPU and I/O loads accompanying updating of the meta-data of the file system that occur on the node where MDS operates
• CPU throughput, I/O throughput, memory capacity, and swap area

To activate a node that accesses the GFS Shared File System, the node must have been set as an MDS node, or the primary MDS node, secondary MDS node, or standby MDS node (or all together) must be activated simultaneously or activated in advance. To stop all nodes set as MDS nodes, all nodes that access the relevant file system must have been stopped.

By setting all nodes that share a file system as MDS nodes (i.e., primary MDS node, secondary MDS node or standby MDS node), each node can be activated or stopped regardless of the state of the other nodes. If both the primary and secondary MDS nodes are stopped during operation, the file system can still be used because standby MDS nodes will be activated as the primary MDS and secondary MDS nodes.

When activating the primary or secondary MDS on a standby MDS node, activation of the primary MDS or secondary MDS may take some time.