Guidelines for VERITAS Volume Manager Software

Consider the following points when you plan VERITAS Volume Manager (VxVM) configurations.

• Enclosure-Based Naming – Enclosure-Based Naming is a feature that was introduced in VxVM version 3.2. If you use Enclosure-Based Naming of devices, ensure that you use consistent device names on all cluster nodes that share the same storage. VxVM does not coordinate these names, so the administrator must ensure that VxVM assigns the same names to the same devices from different nodes. Failure to assign consistent names does not interfere with correct cluster behavior. However, inconsistent names greatly complicate cluster administration and greatly increase the possibility of configuration errors, potentially leading to loss of data.

• Root-disk group – You must create a default root-disk group (rootdg) on each node. The rootdg disk group can be created on the following disks:

  • The root disk, which must be encapsulated

  • One or more local nonroot disks, which you can encapsulate or initialize

  • A combination of root and local nonroot disks

  The rootdg disk group must be local to the node.

• Encapsulation – Disks to be encapsulated must have two disk-slice table entries free.

• Number of volumes – Estimate the maximum number of volumes any given disk device group can use at the time the disk device group is created.

  • If the number of volumes is less than 1000, you can use default minor numbering.

  • If the number of volumes is 1000 or greater, you must carefully plan the way in which minor numbers are assigned to disk device group volumes. No two disk device groups can have overlapping minor number assignments.

• Dirty Region Logging – Using Dirty Region Logging (DRL) decreases volume recovery time after a node failure. Using DRL might decrease I/O throughput.

• Dynamic Multipathing (DMP) – DMP is not supported on Sun Cluster configurations. If you use VxVM in a configuration with multiple paths per node, then you must use another multipathing solution, such as Sun StorEdge Traffic Manager or EMC PowerPath. However, having DMP enabled on systems with only a single path per node poses no problems.