Sun Cluster System Administration Guide for Solaris OS

Overview of Administering Global Devices and the Global Namespace

Administration of Sun Cluster device groups depends on the volume manager that is installed on the cluster. Solaris Volume Manager is “cluster-aware,” so you add, register, and remove device groups by using the Solaris Volume Manager metaset(1M) command. If you are using Veritas Volume Manager (VxVM), you create disk groups by using VxVM commands. You register the disk groups as Sun Cluster device groups with the clsetup utility. When removing VxVM device groups, you use both the clsetup command and VxVM commands.

Note –

For the Solaris 10 OS, global devices are not directly accessible from global-cluster non-voting nodes.

Sun Cluster software automatically creates a raw-disk device group for each disk and tape device in the cluster. However, cluster device groups remain in an offline state until you access the groups as global devices. When administering device groups, or volume manager disk groups, you need to be on the cluster node that is the primary node for the group.

Normally, you do not need to administer the global device namespace. The global namespace is automatically set up during installation and automatically updated during Solaris OS reboots. However, if the global namespace needs to be updated, you can run the cldevice populate command from any cluster node. This command causes the global namespace to be updated on all other cluster node members, as well as on nodes that might join the cluster in the future.

Global Device Permissions for Solaris Volume Manager

Changes made to global device permissions are not automatically propagated to all the nodes in the cluster for Solaris Volume Manager and disk devices. If you want to change permissions on global devices, you must manually change the permissions on all the nodes in the cluster. For example, if you want to change permissions on global device /dev/global/dsk/d3s0 to 644, you must issue the following command on all nodes in the cluster:

# chmod 644 /dev/global/dsk/d3s0

VxVM does not support the chmod command. To change global device permissions in VxVM, consult the VxVM administrator's guide.

Dynamic Reconfiguration With Global Devices

You must consider the following issues when completing dynamic reconfiguration (DR) operations on disk and tape devices in a cluster.

All of the requirements, procedures, and restrictions that are documented for the Solaris DR feature also apply to Sun Cluster DR support. The only exception is for the operating system quiescence operation. Therefore, review the documentation for the Solaris DR feature before using the DR feature with Sun Cluster software. You should review in particular the issues that affect non-network IO devices during a DR detach operation.
Sun Cluster rejects DR remove-board operations on active devices in the primary node. DR operations can be performed on inactive devices in the primary node and on any devices in the secondary nodes.
After the DR operation, cluster data access continues as before.
Sun Cluster rejects DR operations that impact the availability of quorum devices. See Dynamic Reconfiguration With Quorum Devices for more information.

Caution –

If the current primary node fails while you are performing the DR operation on a secondary node, cluster availability is impacted. The primary node will have no place to fail over until a new secondary node is provided.

To perform DR operations on global devices, complete the following steps in the order indicated.

Table 5–1 Task Map: Dynamic Reconfiguration With Disk and Tape Devices


Task	For Instructions
1. If a DR operation that affects an active device group must be performed on the current primary node, switch the primary and secondary nodes before performing the DR remove operation on the device	How to Switch the Primary for a Device Group
2. Perform the DR removal operation on the device being removed	Sun Enterprise 10000 DR Configuration Guide and the Sun Enterprise 10000 Dynamic Reconfiguration Reference Manual in the Solaris 9 on Sun Hardware, and Solaris 10 on Sun Hardware collections.

SPARC: Veritas Volume Manager Administration Considerations

For Sun Cluster software to maintain the VxVM namespace, you must register any VxVM disk group or volume changes as Sun Cluster device group configuration changes. Registering these changes ensures that the namespace on all cluster nodes is updated. Examples of configuration changes that impact the namespace include adding, removing, or renaming a volume. Changing the volume permissions, owner, or group ID also impacts the namespace.

Note –
Never import or deport VxVM disk groups by using VxVM commands after the disk group has been registered with the cluster as a Sun Cluster device group. The Sun Cluster software handles all cases where disk groups need to be imported or be deported.
Each VxVM disk group must have a cluster-wide unique minor number. By default, when a disk group is created, VxVM chooses a random number that is a multiple of 1000 as that disk group's base minor number. For most configurations with only a small number of disk groups, the minor number is sufficient to guarantee uniqueness. The minor number for a newly created disk group might conflict with the minor number of a preexisting disk group that was imported on a different node. In this case, attempting to register the Sun Cluster device group fails. To fix this problem, the new disk group should be given a new minor number that is a unique value and then registered as a Sun Cluster device group.
If you are setting up a mirrored volume, Dirty Region Logging (DRL) can be used to decrease volume recovery time after a node failure. Use of DRL is strongly recommended, although use of DRL could decrease I/O throughput.
VxVM does not support the chmod command. To change global device permissions in VxVM, consult the VxVM administrator's guide.
Sun Cluster 3.2 software does not support the VxVM Dynamic Multipathing (DMP) management of multiple paths from the same node.
If you use VxVM to set up shared disk groups for Oracle RAC, use the cluster functionality of VxVM as described in the Veritas Volume Manager Administrator's Reference Guide. Creating shared disk groups for Oracle RAC differs from creating other disk groups. You must import the Oracle RAC shared disk groups by using vxdg -s. You do not register the Oracle RAC shared disk groups with the cluster framework. To create other VxVM disk groups, see SPARC: How to Create a New Disk Group When Initializing Disks (Veritas Volume Manager).