Veritas™ Volume Manager Administrator's Guide

Tuning guidelines for large systems

On smaller systems (with fewer than a hundred disk drives), tuning is unnecessary. VxVM can adopt reasonable defaults for all configuration parameters. On larger systems, configurations can require additional control over the tuning of these parameters, both for capacity and performance reasons.

Generally, only a few significant decisions must be made when setting up VxVM on a large system. One is to decide on the size of the disk groups and the number of configuration copies to maintain for each disk group. Another is to choose the size of the private region for all the disks in a disk group.

Larger disk groups have the advantage of providing a larger free-space pool for the vxassist command to select from. They also allow for the creation of larger volumes. Smaller disk groups do not require as large a configuration database and so can exist with smaller private regions. Very large disk groups can eventually exhaust the private region size in the disk group. The result is that no more configuration objects can be added to that disk group. At that point, the configuration either has to be split into multiple disk groups, or the private regions have to be enlarged. Each disk in the disk group must be re-initialized. This can involve reconfiguring everything and restoring from backup.