HP Surestore Disk Array 12h - And FC60 System Administrator Manual page 18

Managing the HP SureStore E Disk Array 12H on HP-UX
Tips for Configuring the Disk Array On HP-UX
Configuration
Option
Number of disk
drives
Unallocated disk
array capacity
LVM configuration
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Impact on Performance and Capacity
Performance. Increase the number of disk mechanisms in the disk array
for maximum performance. As the number of individual disks is
increased, the number of potential I/Os that can be performed
simultaneously increases as well. This will improve performance in
environments that place heavy I/O demand on the disk array.
Capacity. The capacity of a disk array that is fully populated with disk
mechanisms can only be increased by replacing lower capacity disks with
higher capacity disks.
Performance. Unallocated capacity is used as additional RAID 0/1
space. The amount of RAID 0/1 space required to maintain optimal
performance is determined by the write working set parameter.
Capacity. To create the maximum amount of storage capacity, allocate
all available capacity to LUNs.
Performance. To improve performance, configure LVM as follows:
Stripe logical volumes across LUNs on different disk arrays.
Including LUNs on different disk arrays will improve throughput by
spreading I/Os across arrays.
Divide LUN access between both disk array controllers. Mapping
every LUN to the same controller does not utilize the two data paths
available on the disk array. The default path is through the primary
disk array controller, but this can be changed to the secondary
controller when adding the physical volume to an LVM volume group.
The process for changing the path differs for each version of HP-UX:
HP-UX 10.1. From the Disk Devices list, select the disk hardware
path through the secondary controller before adding the disk to
a volume group.
HP-UX 10.2. When adding the disk to a volume group, in the
"Creating A Volume Group" dialog change the hardware path to
the secondary controller
Capacity. These LVM configurations have no impact on disk array
capacity configuration.