Migrating to Fabric

A Fibre Channel fabric (one or more switches in a configuration) can provide multiple benefits including independent bandwidth per port, greater reliability, and increased performance.

Before you change your environment to a fabric supported environment, read the following sections carefully. They list the advantages and considerations of migrating to fabric, the requirements for fabric configurations, and examples of the configurations we support with the following host bus adapters:

A5158A PCI Fibre Channel Tachyon TL Adapter
A6684A HSC Fibre Channel Tachlite Adapter
A6685A HSC Fibre Channel Tachlite Adapter
A6795A PCI Fibre Channel Tachyon XL2 Adapter
A6826A PCI-X Dual Port Fibre Channel Adapter

The configuration examples and some of the terminology we used are specific to the Brocade switch. We used this switch only as an example. HP also supports other switches. See the “Supported Platforms, Switches and Devices” link under Fibre Channel HBAs on our web site accessed through the ITRC. Log on to the ITRC web site (http://itrc.hp.com), and click on navigate knowledge trees and response center FAQs. In the Hardware area, navigate the links to networks/mass storage connectivity/fibre channel/technical support.

Important Considerations of Migrating to Fabric

When migrating from a private loop environment to a fabric environment, consider the following advantages.

Reliability

Total removal of LIPs for N_Port (Direct Fabric Attach) devices results in the following:
- No LIP storms.
- No lost frames due to other devices going offline or coming online on the link.
  This activity can cause long delays (approximately 10 sec) while the I/O is timed out and then retried for direct access devices. It can also cause a loss of position for sequential access devices, and the entire operation may need to be retried.
Simpler link level protocol results in fewer chances of encountering hardware, firmware, or software defects in the HBAs.
A fabric environment can provide multiple paths of communication between initiator and the target on the loop. If one path goes down because of loop port/link problems, the switch can determine an alternate path.

Manageability and Fault Isolation

Switches contain management utilities which collect and present a broad range of statistical and error information. This information greatly assists in identifying specific components that are experiencing errors.
Link level faults are isolated to a single link segment on a fabric.
Target devices that are directly connected to the switch no longer need to have loop identifiers (Hard Physical Addresses) configured.

Performance

Removal of FC-AL protocol for N_Port (DFA) devices.
FC-AL protocol overhead is related to frame size and the number of members on the loop. FC-AL protocol can be quite significant for larger loop configurations (loops with more than 30 active nodes). When you move to a Direct Fabric Attach topology, the AL level of protocol is no longer needed or present.
Addition of fabric routing time.
Fabric routing times are generally less than 1 msec (one microsecond). For single switch fabrics or properly configured cascaded switches, the fabric will have no noticeable effect on latency.
Parallel transfer of data.
Fabrics allow parallel transfers of data to and from multiple initiators on the fabric. They also allow parallel transfer of data to and from separate targets at the same time with a single initiator.

Scalability

Fabrics allow you to expand beyond a single loop with a maximum of 126 loop ports to a SAN environment where it is possible to use multiple fabrics and attach virtually unlimited numbers of devices in several configurations.
In addition to attaching devices directly to the fabric or having public loops in the SAN, you can attach an existing (but separate) private loop to the fabric, and have all of the devices managed by the fabric. This configuration creates a highly scalable and modular network of storage devices that you can extend as desired with minor effects to the existing network.

Sharing

Devices, such as tapes, that needed to be configured in a point-to-point configuration in a loop can now be shared with disk devices when they are in a fabric environment.

Device File Addressing Changes

Be aware of the following changes in your device files when you migrate to fabric:

Device file names and iotree paths will change when you replace a private loop with a fabric switch.
Device file names and iotree paths will change when you move a target device from one port on a fabric switch to another port on the switch.
Device files and iotree nodes will change if the switch domain changes.

For more information on device file addressing changes, see the section “Fabric Device Addressing Changes”.

Requirements for Arbitrated Loop and Fabric Support

A5158A PCI Tachyon TL adapter
- HP-UX 11.00 or 11i v1.0 for PA-RISC systems
- HP-UX 11i v1.6 or later for IPF systems
- A5158A HP-UX 11.00 or 11i v1.0 software driver for PA-RISC systems. The driver is available on the web at http://www.software.hp.com and on the HP-UX Application CD, AR0301 and later. The driver is always installed with the HP-UX 11i v1.0 Operating Environment.
- Tachyon patch PHKL_23939 or later for HP-UX 11.00
- Tachyon patch PHKL_23626 or later for HP-UX 11i v1.0
A6684A and A6685A HSC Tachlite adapters
- OS version HP-UX 10.20, 11.00 or 11i v1.0
- A6684A/A6685A 10.20, 11.00 or 11i v1.0 software driver. The driver is available on the web at http://www.software.hp.com and on the HP-UX Application CD, AR0601 and later. The driver is always installed with the HP-UX 11i v1.0 Operating Environment.
- J3630BA Fibre Channel Software Bundle (if not already installed, for 10.20 only)
- PHSS_23581 or later for HP-UX 10.20
- PHKL_17590 or later for HP-UX 10.20
- PHKL_16751 or later for HP-UX 10.20
- Tachyon patch PHKL_23939 or later for HP-UX 11.00
- Tachyon patch PHKL_23626 or later for HP-UX 11i v1.0
A6795A PCI Tachyon XL2 adapter
- OS version HP-UX 11.00 and 11i v1.0
- A6795A HP-UX 11.00 or 11i v1.0 software driver. The driver is available on the web at http://www.software.hp.com and on the HP-UX Application CD, AR1201 or later. The driver is always installed with the HP-UX 11i v1.0 Operating Environment.
- Tachyon patch PHKL_23939 or later for HP_UX 11.00
- Tachyon patch PHKL_23626 or later for HP-UX 11i v1.0
A6826A PCI-X Dual Port adapter
- OS version HP-UX 11i v1.0
- A6826A HP-UX 11i v1.0 software driver. The driver is available on the web at http://www.software.hp.com.
- PHKL_28801 or later for HP_UX 11i v1.0
- PHKL_23445 or later for HP-UX 11i v1.0
Supported hardware

For the latest list of supported hardware and topologies, contact your HP representative, or visit the ITRC web site mentioned on page 6 in this manual.

Restrictions

All target loop devices are required to continue using hard physical addresses.
Remote device or LUN level scanning from IODC is not supported.
fcmsutil option, echo, cannot be used in a fabric configuration.
The maximum number of Tachyon TL hosts that HP recommends on an FL_Port is nine in non-HA configurations and four in HA configurations.