Compaq HSZ80 manual Planning Partitions, Defining a Partition, 40Creating Storagesets

3–40Creating Storagesets

Planning Partitions

Use partitions to divide a storageset or disk drive into smaller pieces, which can be presented to the host as its own storage unit. Figure 3–14shows the conceptual effects of partitioning a single-disk unit.

Partition 1

Partition 2

Partition 3

CXO-5316A-MC

Figure 3–14. 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 percentages 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).