Optimizing Device Performance; Domain Id, Principal Priority, And Domain Id Lock; Stacking - HP StorageWorks SN6000 Installation And Reference Manual

Optimizing device performance

When choosing a topology for a multiple switch fabric, you should also consider the proximity of your
server and storage devices and the performance requirements of your application. Storage applications
such as video distribution, medical record storage/retrieval, or real-time data acquisition can have specific
latency or bandwidth requirements.
The SN6000 Fibre Channel Switch provides the lowest latency of any product in its class. For information
about latency, see "Performance" (page 20). However, the highest performance is achieved on Fibre
Channel switches by keeping traffic within a single switch instead of relying on ISLs. Therefore, for optimal
device performance, place devices on the same switch under the following conditions:
• Heavy I/O traffic between specific server and storage devices.
• Distinct speed mismatch between devices such as the following:
• An 8 Gb/s server and a slower 4 Gb/s storage device
• A high performance server and a slow tape storage device

Domain ID, principal priority, and domain ID lock

The following switch configuration settings affect multiple switch fabrics:
• Domain ID
• Principal priority
• Domain ID lock
The domain ID is a unique number from 1–239 that identifies each switch in a fabric. The principal priority
is a number (1–255) that determines the principal switch which manages domain ID assignments for the
fabric. The switch with the highest principal priority (1 is high, 255 is low) becomes the principal switch. If
the principal priority is the same for all switches in a fabric, the switch with the lowest Worldwide Name
(WWN) becomes the principal switch.
The domain ID lock allows (False) or prevents (True) the reassignment of the domain ID on that switch.
Switches come from the factory with the domain ID set to 1, the domain ID lock set to False, and the
principal priority set to 254. For information about changing the default domain ID, domain ID lock, and
principal priority parameters, see the set config switch command in the HP StorageWorks SN6000
Fibre Channel Switch Command Line Interface Guide.
If you connect a new switch to an existing fabric with its domain ID unlocked, and a domain ID conflict
occurs, the new switch will isolate as a separate fabric. You can remedy this by resetting the new switch or
taking it offline then putting it back online. The principal switch will reassign the domain ID and the switch
will join the fabric.
NOTE: Domain ID reassignment is not reflected in zoning that is defined by domain ID/port number pair
or Fibre Channel address. You must reconfigure zones that are affected by domain ID reassignment. To
prevent zoning definitions from becoming invalid under these conditions, lock the domain IDs. Domain ID
reassignment has no effect on zone members defined by WWN.

Stacking

You can connect up to six HP StorageWorks SN6000 Fibre Channel Switches together through the XPAK
ports, thus preserving the SFP ports for devices. This is called stacking. The following 2-, 3-, 4-, 5-, and
6-switch stacking configurations are recommended for best performance and redundancy. Each XPAK port
contributes 12.75 GB of bandwidth between chassis in each direction. This is equivalent to three SFP
connections operating at 4 Gb/s. If you upgrade the XPAK ports to 20 Gb/s, this is equivalent to three
HP StorageWorks SN6000 Fibre Channel Switch Installation and Reference Guide 23