HP StorageWorks Fabric OS 5.X Administrator 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.