CFS Administration
This section describes some of the major aspects of cluster file system administration and the ways in which it differs from single-host VxFS administration.
CFS Resource Management Commands
To make resources easier to manage, five CFS administrative commands were introduced in this release. The commands are:
- cfscluster---cluster configuration command
- cfsmntadm---adds, deletes, modifies, and sets policy on cluster mounted file systems
- cfsdgadm---adds or deletes shared disk groups to/from a cluster configuration
- cfsmount/cfsumount---mounts/unmounts a cluster file system on a shared volume
CFS Commands
The mount and fsclustadm commands are also important for configuring cluster file systems.
mount
The mount command with the –o cluster option lets you access shared file systems. See the mount_vxfs(1M) manual page for information on allowable mount options.
fsclustadm
The fsclustadm command reports various attributes of a cluster file system. Using fsclustadm you can show and set the primary node in a cluster, translate node IDs to host names and vice versa, list all nodes that currently have a cluster mount of the specified file system mount point, and determine whether a mount is a local or cluster mount. The fsclustadm command operates from any node in a cluster on which the file system is mounted, and can control the location of the primary for a specified mount point. See the fsclustadm(1M) manual page for information on usage.
fsadm
The fsadm command must be run from the primary node; it fails if invoked on secondaries. See the fsadm(1M) manual page for information on allowable mount options.
Running Commands Safely in a Cluster Environment
Any UNIX command that can write to a raw device must be used carefully in a shared environment to prevent data from being corrupted. For shared VxVM volumes, CFS provides protection by reserving the volumes in a cluster to prevent VxFS commands, such as fsck and mkfs, from inadvertently damaging a mounted file system from another node in a cluster. However, commands such as dd execute without any reservation, and can damage a file system mounted from another node. Before running this kind of command on a file system, be sure the file system is not mounted on a cluster. You can run the mount command to see if a file system is a shared or local mount.
Time Synchronization for 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.
Growing a Cluster File System
There is a master node for CVM as well as a primary for CFS. When growing a file system, you grow the volume from the CVM master, and then grow the file system from the CFS primary. The CVM master and the CFS primary can be two different nodes. To determine the primary file system in a cluster, enter:
# fsclustadm –v showprimary mount_point
To determine if the current node is the master CVM node, enter:
# vxdctl -c mode
To actually increase the size of the file system, run the following two commands. On the master CVM node, enter:
# vxassist –g shared_disk_group growto volume_name newlength
On the CFS primary, enter:
# fsadm –F vxfs –b newsize –r device_name mount_point
The fstab File
In the /etc/fstab file, do not specify any cluster file systems to mount-at-boot because mounts initiated from fstab occur before cluster configuration begins. For cluster mounts, use the VCS configuration file to determine which file systems to enable following a reboot.
Distributing the Load on a Cluster
Distributing the workload in a cluster provides performance and failover advantages. Because each cluster mounted file system can have a different node as its primary, CFS lets you easily distribute the load in a cluster.
For example, if you have eight file systems and four nodes, designating two file systems per node as the primary would be beneficial. Primaryship is determined by which node first mounts the file system. You can also use the fsclustadm to designate a CFS primary. The fsclustadm setprimary command can also define the order in which primaryship is assumed if the current primary fails. After setup, the policy is in effect as long as one or more nodes in the cluster have the file system mounted.
Using GUIs
Use the VERITAS Enterprise Administrator (VEA) for various VxFS functions such as making and mounting file systems, on both local and cluster file systems.
With SFCFS HA, you can use the VCS Cluster Manager GUI to configure and monitor CFS. The VCS GUI provides log files for debugging LLT and GAB events.
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