Cluster File System Architecture
About CFS
Synchronizing Time on Cluster File Systems
CFS requires that the system clocks on all nodes are synchronized using some external component such as the Network Time Protocol (NTP) daemon. If the nodes are not in sync, timestamps for creation (ctime) and modification (mtime) may not be consistent with the sequence in which operations actually happened.
Distributing Load on a Cluster
For example, if you have eight file systems and four nodes, designating two file systems per node as the primary is beneficial. The first node that mounts a file system becomes the primary for that file system.
You can also use the fsclustadm command to designate a CFS primary. The fsclustadm setprimary command can be used to change the primary. This change to the primary is not persistent across unmounts or reboots. The change is in effect as long as one or more nodes in the cluster have the file system mounted. The primary selection policy can also be defined by an HP Serviceguard attribute associated with the CFS mount resource.
File System Tuneables
Tuneable parameters are updated at the time of mount using the tunefstab file or vxtunefs command. The file system tunefs parameters are set to be identical on all nodes by propagating the parameters to each cluster node. When the file system is mounted on the node, the tunefs parameters of the primary node are used. The tunefstab file on the node is used if this is the first node to mount the file system. HP recommends that this file be identical on each node.
Single Network Link and Reliability
In some environments, you may prefer using a single private link, or a pubic network, for connecting nodes in a cluster - despite the loss of redundancy if a network failure occurs. The benefits of this approach include simpler hardware topology and lower costs; however, there is obviously a tradeoff with high availability.
I/O Error Handling Policy
I/O errors can occur for several reasons, including failures of FibreChannel links,
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