Compaq StorageWorks HSG60 ACS Solution Software V8.6 for Compaq Tru64 UNIX Installation and Configuration Guide

2–20 HSG60 ACS Solution Software Version 8.6 for Compaq Tru64 UNIX Installation and Configuration Guide
You can create up to eight partitions per storageset (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. Partitions are separately addressable storage units, therefore, 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:
■ 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.
■ RAIDsets and stripesets—the controller allocates the largest whole number of
stripes that are less than or equal to the percentage you specify.
❏ Stripesets—the stripe size = chunk size × number of members.
❏ RAIDsets—the stripe size = chunk size × (number of members minus 1)
An unpartitioned storage unit has more capacity than a partition that uses the whole
unit because each partition requires a small amount of disk space for metadata.
Guidelines for Partitioning Storagesets and Disk Drives
Keep these points in mindwhen planning partitions for storagesets and disk drives:
■ A storageset or disk drive can contain up to eight partitions.
■ In transparent failover mode, all partitions of a particular container must be on the
same host port. Partitions cannot be split across host ports.
■ In multiple-bus failover mode, all the partitions of a particular container must be on the
same controller. Partitions cannot be split across controllers.
■ Partitions cannot be combined into storagesets. For example, you cannot divide a disk
drive into three partitions, then combine those partitions into a RAIDset.
■ Just as with storagesets, you do not have to assign unit numbers to partitions until
you are ready to use them.
■ The CLONE utility cannot be used with partitioned mirrorsets or partitioned
stripesets (See “Cloning Data for Backup,” page 8–2 for details about cloning.))