HP P9000 Provisioning for Mainframe Systems User Guide (AV400-96369, October 2011)

When to use fixed-sized provisioning
Fixed-sized provisioning is a best fit in the following scenarios:
• In mainframe systems, and on open systems in some scenarios.
Custom-sized provisioning
Custom-sized (or variable-sized) provisioning has more flexibility than fixed-sized provisioning and
is the traditional storage-based volume management strategy typically used to organize storage
space on a server. It requires fewer logical devices, but larger ones.
To create custom-sized volumes on a storage system, an administrator first creates array groups
of any RAID level from parity groups. Then, volumes of the desired size are created from these
individual array groups. These volumes are then individually mapped to one or more host ports
as a logical unit.
Following are two scenarios where custom-sized provisioning is an advantage:
• In fixed-sized provisioning, when several frequently accessed files are located on the same
volume and one file is being accessed, users cannot access the other files because of logical
device contention. If the custom-sized feature is used to divide the volume into several small
volumes and I/O workload is balanced (each file is allocated to each volume), then access
contention is reduced and access performance is improved.
• In fixed-sized provisioning, not all of the capacity may be used. Some capacity on the volume
may remain inaccessible to other users. If the custom-sized feature is used, smaller volumes
can be created that do not waste capacity.
To change the size of a volume already in use, you first create a new volume larger (if possible)
than the old one, and then move the contents of the old volume to the new one. The new volume
would be remapped on the server to take the mount point of the old one, which is retired.
A disadvantage is that this manual intervention can become costly and tedious and this provisioning
strategy is appropriate only in certain scenarios.
When to use custom-sized provisioning
Custom-sized provisioning is a best fit in the following scenario:
• In both mainframe and open systems environments.
• When you want to manually control and monitor your storage resources and usage scenarios.
Virtual LVI software is used to configure custom-sized provisioning. For detailed information, see
(page 26).
Basic provisioning workflow
The following illustrates the basic provisioning workflow:
Basic provisioning 9