HP Storage Provisioning Manager (SPM) version 2.3 User Guide

3PAR calculation (CPG based pools)SPM capacity value
when a volume gets provisioned in a pool, that much
capacity becomes unavailable for other pools).
The logical capacity used by the CPG. This includes
volumes as well as snapshot and admin space (for
example, RAID overhead and cruft).
Committed capacity
Calculated as the sum of all volumes' subscribed capacities.
Hence SPM reports logical capacity.
Subscribed capacity
The difference between the CPG's physical capacity and
its committed capacity.
Available capacity
SPM does not attempt to create new volumes in a pool if the HP 3PAR StoreServ Storage System
reports that the pool’s available capacity is not sufficient to contain the requested volume. In cases
where a number of volumes have been deleted from the pool, the HP 3PAR StoreServ Storage
System reports that the available capacity is smaller than would be expected given the active
volumes within the pool. This occurs because HP 3PAR StoreServ Storage Systems do not reclaim
space from deleted volumes automatically, meaning that deleted volumes continue to take up space
in a pool until the system administrator manually reclaims that space. SPM cannot reclaim the
space consumed by deleted volumes, so if such a situation arises, system administrators must log
into the HP 3PAR StoreServ Storage System and reclaim the space manually by compacting the
relevant pool.
Volume capacity
SPM tracks capacity and committed capacity for volumes, where capacity is the overall capacity
of the volume in bytes and committed capacity is the number of bytes that have actually been
reserved for the volume.
Capacity in SPM maps to the usable capacity of the volume accounting for RAID overhead and
administrative space. For thinly provisioned volumes, this may be greater than the committed
capacity. SPM's committed capacity for thinly provisioned volumes the number of provisioned
blocks times the block size. For thickly provisioned volumes, the committed capacity is the same
as the capacity.
The HP 3PAR StoreServ Storage System reports all storage capacities in binary units proposed by
the International Electrotechnical Commission (IEC) instead of the International System of Units (SI)
decimal units. As an example, 20GiB in binary units would be equivalent to 21.47GB in decimal
units. Matrix customers will notice a capacity reporting difference when using the HP 3PAR StoreServ
Storage System if not using SPM. SPM helps the customer address this unit conversion issue by
allowing the customer to set the preferred capacity reporting units. It is recommended that the
preferences in SPM be set to decimal units.
Understanding HP 3PAR StoreServ Storage System volume creation/growth
During storage service provisioning, a set of service requirements are drawn from the storage
service template and additional requirements. SPM uses these requirements to select a set of
candidate volumes to offer for service fulfillment. SPM uses capacity information from the array,
both for volumes and storage pools, to generate the candidates.
The candidates may include existing volumes of the appropriate size, existing volumes that would
need to grow, or as yet uncreated volumes. If a given candidate volume does not match the service's
requirements exactly, provisioning automation is required to make the change on the array to fulfill
the service. This automation is divided up into discrete steps, like “create a volume” or “grow a
volume” as well as “update a volume's presentation settings”.
SPM uses the importing credentials and SMI-S protocol to access the array to make the automated
changes.
Understanding HP 3PAR StoreServ Storage System volume creation/growth 81