In the GFS Shared File System, up to two nodes can share one file system simultaneously.
File system processing can continue even if the node (on which MDS manages file system meta-data) fails. Two nodes that operate MDS are selected, the node that wants to operate primary MDS is made primary MDS node (on which the primary MDS usually operates), and the node that wants to operate secondary MDS is set as secondary MDS node (on which the secondary MDS usually operates).
See
For details on the effects of MDS node settings, see "3.1 MDS Failure Recovery"
As previously described in "4.3.1 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
Note
MDS receives requests from all nodes sharing a file system and then updates the meta-data. Therefore, install at least two CPUs on nodes on which MDS may operate.
Note
When activating the secondary MDS, activation of the primary MDS may take the time for a while.
