Guidelines for Veritas Volume Manager Software

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

• Accessibility to nodes – You must configure all volume-manager disk groups as either Sun Cluster device groups or as local-only disk groups. If you do not configure the disk group in one of these ways, the devices in the disk group will not be accessible to any node in the cluster.

  • A device group enables a secondary node to host multihost disks if the primary node fails.

  • A local-only disk group functions outside the control of Sun Cluster software and can be accessed from only one node at a time.

• Enclosure-Based Naming – 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 – The creation of a root disk group is optional.

  A root 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 root disk group must be local to the Solaris host.

• Simple root disk groups – Simple root disk groups, which are created on a single slice of the root disk, are not supported as disk types with VxVM on Sun Cluster software. This is a general VxVM software restriction.

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

• Number of volumes – Estimate the maximum number of volumes any given device group can use at the time the 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 device group volumes. No two device groups can have overlapping minor number assignments.

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

• Dynamic Multipathing (DMP) – The use of DMP alone to manage multiple I/O paths per Solaris host to the shared storage is not supported. The use of DMP is supported only in the following configurations:

  • A single I/O path per host is configured to the cluster's shared storage.

  • A supported multipathing solution is used, such as Solaris I/O multipathing software (MPxIO), EMC PowerPath, or Hitachi HDLM, that manages multiple I/O paths per host to the shared cluster storage.

• ZFS – Root-disk encapsulation is incompatible with a ZFS root file system.

See your VxVM installation documentation for additional information.