HP Array Controller HSG V8.7 Software - Manual (Page 115)

Creating Storagesets 3–37
Planning Partitions
Use partitions to divide a storageset or disk drive into smaller pieces,
which can each be presented to the host as its own storage unit. Figure
3–17 shows the conceptual effects of partitioning a single-disk unit.
Figure 3–17 Partitioning a Single-Disk Unit
You can create up to eight partitions per disk drive, RAIDset, mirrorset,
stripeset, or striped mirrorset. Each partition has its own unit number so
that the host can send I/O requests to the partition just as it would to
any unpartitioned storageset or device. Because partitions are
separately-addressable storage units, you can partition a single
storageset to service more than one user group or application.
Defining a Partition
Partitions are expressed as a percentage of the storageset or single disk
unit that contains them. For mirrorsets and single disk units, the
controller allocates the largest whole number of blocks that are equal to
or less than the percentage you specify. For RAIDsets and stripesets,
the controller allocates the largest whole number of stripes that are less
than or equal to the percentage you specify. For stripesets, the stripe
size = chunk size x number of members. For RAIDsets, the stripe size =
chunk size x (number of members-1).
An unpartitioned storage unit has more capacity than a partition that
uses the whole unit because each partition requires five blocks of
administrative metadata. Thus, a single disk unit that contains one
partition can store n-5 blocks of user or application data.
See “Partitioning a Storageset or Disk Drive,” page 3–61, for
information on manually partitioning a storageset or single-disk unit.
Partition 1
Partition 2
Partition 3
CXO-5316A-MC