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Sun Cluster 3.0 12/01 System Administration Guide

3.1 Administering Global Devices and the Global Namespace Overview

Administration of Sun Cluster disk device groups depends on the volume manager installed on the cluster. Solstice DiskSuite is "cluster-aware," so you add, register, and remove disk device groups by using the Solstice DiskSuite metaset(1M) command. With VERITAS Volume Manager (VxVM), you create disk groups by using VxVM commands. Then you register the disk groups as Sun Cluster disk device groups through the scsetup(1M) utility. When removing VxVM disk device groups, you use both the scsetup utility and VxVM commands.

Sun Cluster software automatically creates a rawdisk device group for each disk and tape device in the cluster. However, these cluster device groups remain in an offline state until you access them as global devices. When administering disk 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 because the global namespace is automatically set up during installation and automatically updated during Solaris operating environment reconfiguration reboots. However, if the global namespace needs to be regenerated or updated, you can run the scgdevs(1M) command from any cluster node. This 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.

3.1.1 Global Device Permissions for Solstice DiskSuite

Changes made to global device permissions are not automatically propagated to all the nodes in the cluster for Solstice DiskSuite 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 execute

# chmod 644 /dev/global/dsk/d3s0

on all nodes in the cluster.

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

3.1.2 Dynamic Reconfiguration With Global Devices

There are a few issues you must consider when completing dynamic reconfiguration (DR) operations on disk and tape devices in a cluster.

Caution - 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 3-1 Task Map: Dynamic Reconfiguration with Disk and Tape Devices

Task 

For Instructions, Go To... 

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. 

"3.3.18 How to Switch the Primary for a Device Group"

2. Perform the DR remove operation on the device being removed. 

Sun Enterprise 10000 Dynamic Reconfiguration User Guide and the Sun Enterprise 10000 Dynamic Reconfiguration Reference Manual (from the Solaris 8 on Sun Hardware collection)

3.1.3 VERITAS Volume Manager Administration Considerations

For Sun Cluster to maintain the VxVM namespace, you must register any VxVM disk group or volume changes as Sun Cluster disk 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; and changing the volume permissions, owner, or group ID.

Note -

Never import or deport VxVM disk groups using VxVM commands once the disk group has been registered with the cluster as a Sun Cluster disk device group. The Sun Cluster software will handle all cases where disk groups need to be imported or 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, this is sufficient to guarantee uniqueness. However, it is possible that the minor number for a newly-created disk group will conflict with the minor number of a pre-existing disk group imported on a different cluster node. In this case, attempting to register the Sun Cluster disk device group will fail. 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 disk 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 it could decrease I/O throughput.

3.1.3.1 Creating Shared Disk Groups for Oracle Parallel Server/Real Application Clusters

If you use VxVM to set up shared disk groups for Oracle Parallel Server/Real Application Clusters, use the cluster functionality of VxVM as described in the VERITAS Volume Manager Administrator's Reference Guide. Differences between creating shared disk groups for Oracle Parallel Server/Real Application Clusters and creating other disk groups include the following items.

To create other VxVM disk groups, see "3.3.5 How to Create a New Disk Group When Initializing Disks (VERITAS Volume Manager)".