HP Surestore Disk Array 12h and FC60 - Manual (Page 72)

72 Array Design Considerations
enclosures can be added incrementally (up to six) as storage requirements grow. Multiple
SCSI channels also increase data throughput. This increased data throughput occurs as a
result of the controller’s ability to transfer data simultaneously over multiple data paths
(channels). The more channels used, the faster the data throughput.
Disk Enclosure Bus Configuration
The disk enclosure can connect to either one or two SCSI channels, depending on its bus
configuration. Disk enclosure design allows the backplane bus to be split from a single bus
into two separate SCSI busses. When the backplane is operating as a single bus it is
referred to as full-bus mode; when the bus is split into two separate buses it is referred to
as split-bus mode. When in full-bus mode, one SCSI channel connects to all of the ten disk
modules. If the enclosure is configured for split-bus mode, five disk modules are connected
to each of the two separate buses and a separate SCSI channel connects to each of the
BCCs. See
"Installation" on page 143 for more information.
When using split-bus mode, the maximum number of disk enclosures is limited to three
(each disk enclosure uses two channel connections). If the storage capacity needs to be
increased by adding more disk enclosures, the array will need to be reconfigured.
Reconfiguring the array requires shutting down the host system, powering down the array,
installing additional disk enclosures, and reconfiguring and recabling all enclosures.
RAID, LUNs, and Global Hot Spares
In addition to the above hardware configuration considerations, the RAID level and LUN
structure has considerable impact on high availability, performance, and storage capacity.
For information on how RAID level, LUNs, and hot spares affect the performance of a disk
array, see
"Disk Array High Availability Features" on page 47 .
High Availability
If your application requires high availability, you should implement the options discussed
here.The Disk Array FC60 is fully qualified to run MC/ServiceGuard and MC/LockManager.
To work in these environments, a high availability configuration must be used. To configure