3PAR InForm® OS 2.3.1 Concepts Guide (320-200112 Rev B, February 2010)

9.3
Precautions and Planning
InForm OS Version 2.3.1 3PAR InForm OS Concepts Guide
9.2 Precautions and Planning
A Common Provisioning Group (CPG) creates a virtual pool of logical disks that allows up to
4,095 volumes to share the CPG's resources and allocate space on demand. However, CPGs still
require careful planning and monitoring to prevent them from becoming so large that they set
off the system's built-in safety mechanisms. These safety mechanisms are designed to prevent a
CPG from consuming all free space on the system, but they only work properly on systems that
are planned carefully and monitored closely.
9.2.1 Growth Increments, Warnings, and Limits
You can create several types of volumes that draw space from the CPG's logical disk pool as
needed. When creating a CPG, set a growth increment and an optional growth warning and
growth limit to restrict the CPG's growth and maximum size. It is important to plan the CPG's
growth increment, growth warning, and growth limit carefully and then continue to monitor
the CPG closely over time.
CAUTION: Use caution in planning CPGs. The system does not prevent you from
setting growth warnings or growth limits that exceed the amount of currently
available storage on a system. When volumes associated with a CPG use all space
available to that CPG, any new writes to TPVVs associated with the CPG will fail
and/or snapshot volumes associated with the CPG may become invalid or stale.
Under these conditions, some host applications do not handle write failures
gracefully and may produce unexpected failures.
NOTE: By default, the growth warning and growth limit are set to none, which
effectively disables these safety features.