HP StorageWorks Fabric OS 5.X Procedures User Guide (AA-RVHWB-TE, September 2005)

Fabric OS 5.x administrator guide 165
For dynamic long-distance links, you can approximate the number of buffer credits using the following
formula:
Buffer credits = [(distance in km) * (data rate) * 1000]/2112
The data rate is 1.0625 for 1Gbps, 2.125 for 2 Gbps, and 4.25 for 4 Gbps and Fibre Channel. This
formula provides the minimum number of credits allowed to a given port; the actual number will likely be
higher.
Configuring an extended ISL
Before configuring the ISL, ensure that the following conditions are met:
Extended ISL support for HP StorageWorks 1 GB switches is limited as follows:
Extended ISLs are not supported between HP StorageWorks 1 GB switches and other HP
StorageWorks models.
To support extended ISLs between HP StorageWorks 1 GB switches, the
fabric.ops.mode.longDistance parameter must be set to 1 on all switches in the fabric.
Each switch must be disabled before setting this parameter.
For fabrics that contain a mix of HP StorageWorks models, the fabric.ops.mode.longDistance
parameter must be set to 0 (the default). Under certain circumstances (for example, if you want
extended distance between Bloom-based switches) this mode needs to be enabled (set to 1) on
switches running Fabric OS 3.x or 4.x. Talk to your switch provider for details.
The ports on both ends of the ISL must have the same configuration.
Use only qualified SFPs.
1. Connect to the switch and log in as admin.
2. If the fabric contains a mix of switches, use the configure command to make sure the fabric-wide
configuration parameter fabric.ops.mode.longDistance is set to 0 on all switches in the fabric.
If the fabric contains HP StorageWorks 1-GB switches with extended ISLs, use the switchDisable
command to disable the switch, and then use the configure command to set the fabric-wide
configuration parameter fabric.ops.mode.longDistance to 1 on all switches in the fabric.
Table 32 Extended ISL modes: switches with Condor ASIC.
Mode Buffer Allocation Distance at
1 Gbps
Distance at
2 Gbps
Distance at
4 Gbps
Earliest Fabric
OS release
Extended fabrics
license required?
1 Gbps 2 Gbps 4 Gbps
L0 5 (26)
2
5 (26) 2.5 km 10 km 5 km 2 km All No
LE 11 16 10 km N/A 5 km 5 km 3.x, 4.x No
L0.5 18 31 56 25 km 25 km 25 km 3.1.0, 4.1.0,
4.x, 5.x
Yes
L1 31 56 106 50 km 50 km 50 km All Yes
L12 56 106 206 100 km 100 km 100 km All Yes
LD
1
Auto Auto Auto Auto Auto Auto 3.1.0, 4.1.0,
4.4.0, 5.x
(depending on
the model)
Yes
1
The dynamic long-distance (LD) mode configures the number of buffer credits required, based on the actual link distance.
2
For each data channel (in this case, there are 4) there are 5 credits, plus 6 extra credits.