The 48-port and 24-port 4-Gbps, and all 8-Gbps Fibre Channel switching
modules support oversubscription on switches with shared rate mode
configurations. By default, all 48-port and 24-port 4-Gbps, and 8-Gbps Fibre
Channel switching modules have restrictions on oversubscription ratios enabled.
As of Cisco SAN-OS Release 3.1(1) and NX-OS Release 4.1(1), you can disable
restrictions on oversubscription ratios.
Table 1
describes the bandwidth allocation for oversubscribed interfaces configured in
shared mode on the 4-Gbps and 8-Gbps modules.
Table 9. Bandwidth Allocation for Oversubscribed Interfaces
Switching Module
|
Configured Speed
|
Reserved Bandwidth (Gbps)
|
Maximum Bandwidth (Gbps)
|
Ratios disabled
|
Ratios enabled
|
24-Port 8-Gbps Fibre Channel Module
|
Auto 8 Gbps
|
0.8
|
0.8
|
8
|
Auto Max 4 Gbps
|
0.4
|
0.4
|
4
|
Auto Max 2 Gbps
|
0.2
|
0.2
|
2
|
4/44-Port 8-Gbps Host-Optimized Fibre Channel Module
|
8 Gbps
|
0.87
|
0.16
|
8
|
Auto Max 4 Gbps
|
0.436
|
0.08
|
4
|
Auto Max 2 Gbps
|
0.218
|
0.04
|
2
|
1 Gbps
|
0.109
|
0.02
|
1
|
48-port 4-Gbps Fibre Channel switching module
|
Auto 4 Gbps
|
0.8
|
0.09
|
4
|
Auto Max 2 Gbps
|
0.4
|
0.045
|
2
|
1 Gbps
|
0.2
|
0.0225
|
1
|
24-port 4-Gbps Fibre Channel switching module
|
Auto 4 Gbps
|
1
|
0.27
|
4
|
Auto Max 2 Gbps
|
0.5
|
0.135
|
2
|
1 Gbps
|
0.25
|
0.067
|
1
|
All ports in the 48-port and 24-port 4-Gbps modules can be configured
to operate at 4 Gbps in shared mode even if other ports in the port group are
configured in dedicated mode, regardless of available bandwidth. However, when
oversubscription ratio restrictions are enabled, you may not have all shared
4-Gbps module ports operating at 4 Gbps.
All ports in the 48-port, 32-Port, and 24-port 8-Gbps modules can be
configured to operate at 8 Gbps in shared mode even if other ports in the port
group are configured in dedicated mode, regardless of available bandwidth.
However, when oversubscription ratio restrictions are enabled you may not have
all shared 8-Gbps module ports operating at 8 Gbps.
On the 48-port, 32-Port, and 24-port 8-Gbps modules, if you have
configured one 8-Gbps dedicated port in one port group, no other ports in the
same port group can be configured to operate at 8-Gbps dedicated mode. You can
have any number of 8-Gbps shared and 4-Gbps dedicated or shared ports. On the
4/44-port 8-Gbps module, only one port per port group can be configured in
8-Gbps dedicated or shared mode.
In the following example, each of the 4 ports already have 500 credits
and you have 2150 remaining for the port group. So, in all 4150 credits:
switch(config-if)# show port-resources module 1
Module 1
Available dedicated buffers for global buffer #0 [port-group 1] are 2150
Available dedicated buffers for global buffer #1 [port-group 2] are 2150
Available dedicated buffers for global buffer #2 [port-group 3] are 2150
Available dedicated buffers for global buffer #3 [port-group 4] are 2148
Available dedicated buffers for global buffer #4 [port-group 5] are 2150
Available dedicated buffers for global buffer #5 [port-group 6] are 2150
Available dedicated buffers for global buffer #6 [port-group 7] are 2150
Available dedicated buffers for global buffer #7 [port-group 8] are 650
Available dedicated buffers for global buffer #8 [port-group 9] are 2150
Available dedicated buffers for global buffer #9 [port-group 10] are 2150
Available dedicated buffers for global buffer #10 [port-group 11] are 2150
Available dedicated buffers for global buffer #11 [port-group 12] are 2150
Port-Group 1
Total bandwidth is 64.0 Gbps
Allocated dedicated bandwidth is 64.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc1/1 500 16.0 dedicated
fc1/2 500 16.0 dedicated
fc1/3 500 16.0 dedicated
fc1/4 500 16.0 dedicated
Port-Group 6
Total bandwidth is 64.0 Gbps
Allocated dedicated bandwidth is 64.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc4/21 4090 16.0 dedicated
fc4/22 10 16.0 dedicated
fc4/23 10 16.0 dedicated
fc4/24 10 16.0 dedicated
In the following example, a 24-port 4-Gbps module has oversubscription
ratios enabled and three dedicated ports in one port group operating at 4-Gbps.
No other ports in the same port group can be configured to operate at 4 Gbps.
switch# show port-resources module 8
Module 8
Available dedicated buffers are 5478
Port-Group 1
Total bandwidth is 12.8 Gbps
Total shared bandwidth is 0.8 Gbps
Allocated dedicated bandwidth is 12.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc8/1 16 4.0 dedicated
fc8/2 16 4.0 dedicated
fc8/3 16 4.0 dedicated
fc8/4 (out-of-service)
fc8/5 (out-of-service)
fc8/6 (out-of-service)
For dedicated ports, oversubscription ratio restrictions do not apply
to the shared pool in port groups. So if oversubscription ratio restrictions
are disabled, and you have configured three 4-Gbps dedicated ports in one port
group, then you can configure all other ports in the same port group to operate
at a shared rate of 4 Gbps.
In the following example, a 48-port module has a group of six ports,
four dedicated ports are operating at 8 Gbps, and the two shared ports are also
operating at 8 Gbps:
switch# show port-resources module 5
Module 5
Available dedicated buffers for global buffer #0 [port-group 1] are 3970
Available dedicated buffers for global buffer #1 [port-group 2] are 3970
Available dedicated buffers for global buffer #2 [port-group 3] are 3970
Available dedicated buffers for global buffer #3 [port-group 4] are 3970
Available dedicated buffers for global buffer #4 [port-group 5] are 3058
Available dedicated buffers for global buffer #5 [port-group 6] are 3058
Available dedicated buffers for global buffer #6 [port-group 7] are 3970
Available dedicated buffers for global buffer #7 [port-group 8] are 3970
Port-Group 1
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/1 32 8.0 shared
fc5/2 32 8.0 shared
fc5/3 32 8.0 shared
fc5/4 32 8.0 shared
Port-Group 2
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/5 32 8.0 shared
fc5/6 32 8.0 shared
fc5/7 32 8.0 shared
fc5/8 32 8.0 shared
Port-Group 3
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/9 32 8.0 shared
fc5/10 32 8.0 shared
fc5/11 32 8.0 shared
fc5/12 32 8.0 shared
Port-Group 4
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/13 32 8.0 shared
fc5/14 32 8.0 shared
fc5/15 32 8.0 shared
fc5/16 32 8.0 shared
Port-Group 5
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 16.4 Gbps
Allocated dedicated bandwidth is 16.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/17 32 8.0 shared
fc5/18 32 8.0 shared
fc5/19 500 8.0 dedicated
fc5/20 500 8.0 dedicated
Port-Group 6
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 16.4 Gbps
Allocated dedicated bandwidth is 16.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/21 500 8.0 dedicated
fc5/22 500 8.0 dedicated
fc5/23 32 8.0 shared
fc5/24 32 8.0 shared
Port-Group 7
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/25 32 8.0 shared
fc5/26 32 8.0 shared
fc5/27 32 8.0 shared
fc5/28 32 8.0 shared
Port-Group 8
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc5/29 32 8.0 shared
fc5/30 32 8.0 shared
fc5/31 32 8.0 shared
fc5/32 32 8.0 shared
switch# show port-resources module 13
Module 13
Available dedicated buffers for global buffer #0 [port-group 1] are 3880
Available dedicated buffers for global buffer #1 [port-group 2] are 3880
Available dedicated buffers for global buffer #2 [port-group 3] are 3880
Available dedicated buffers for global buffer #3 [port-group 4] are 3056
Available dedicated buffers for global buffer #4 [port-group 5] are 3880
Available dedicated buffers for global buffer #5 [port-group 6] are 3880
Available dedicated buffers for global buffer #6 [port-group 7] are 3880
Available dedicated buffers for global buffer #7 [port-group 8] are 3880
Port-Group 1
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/1 32 8.0 shared
fc13/2 32 8.0 shared
fc13/3 32 8.0 shared
fc13/4 32 8.0 shared
fc13/5 32 8.0 shared
fc13/6 32 8.0 shared
Port-Group 2
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/7 32 8.0 shared
fc13/8 32 8.0 shared
fc13/9 32 8.0 shared
fc13/10 32 8.0 shared
fc13/11 32 8.0 shared
fc13/12 32 8.0 shared
Port-Group 3
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/13 32 8.0 shared
fc13/14 32 8.0 shared
fc13/15 32 8.0 shared
fc13/16 32 8.0 shared
fc13/17 32 8.0 shared
fc13/18 32 8.0 shared
Port-Group 4
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 0.4 Gbps
Allocated dedicated bandwidth is 32.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/19 250 8.0 dedicated
fc13/20 250 8.0 dedicated
fc13/21 250 8.0 dedicated
fc13/22 250 8.0 dedicated
fc13/23 32 8.0 shared
fc13/24 32 8.0 shared
Port-Group 5
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/25 32 8.0 shared
fc13/26 32 8.0 shared
fc13/27 32 8.0 shared
fc13/28 32 8.0 shared
fc13/29 32 8.0 shared
fc13/30 32 8.0 shared
Port-Group 6
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/31 32 8.0 shared
fc13/32 32 8.0 shared
fc13/33 32 8.0 shared
fc13/34 32 8.0 shared
fc13/35 32 8.0 shared
fc13/36 32 8.0 shared
Port-Group 7
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/37 32 8.0 shared
fc13/38 32 8.0 shared
fc13/39 32 8.0 shared
fc13/40 32 8.0 shared
fc13/41 32 8.0 shared
fc13/42 32 8.0 shared
Port-Group 8
Total bandwidth is 32.4 Gbps
Total shared bandwidth is 32.4 Gbps
Allocated dedicated bandwidth is 0.0 Gbps
--------------------------------------------------------------------
Interfaces in the Port-Group B2B Credit Bandwidth Rate Mode
Buffers (Gbps)
--------------------------------------------------------------------
fc13/43 32 8.0 shared
fc13/44 32 8.0 shared
fc13/45 32 8.0 shared
fc13/46 32 8.0 shared
fc13/47 32 8.0 shared
fc13/48 32 8.0 shared
...
When disabling restrictions on oversubscription ratios, all ports in
shared mode on 48-port and 24-port 4-Gbps or any 8-Gbps Fibre Channel switching
modules must be shut down. When applying restrictions on oversubscription
ratios, you must take shared ports out of service.
Note |
When restrictions on oversubscription ratios are disabled, the
bandwidth allocation among the shared ports is proportionate to the configured
speed. If the configured speed is auto on Generation 2 modules, then bandwidth
is allocated assuming a speed of 4 Gbps. For example, if you have three shared
ports configured at 1, 2, and 4 Gbps, then the allocated bandwidth ratio is
1:2:4.
As of Cisco SAN-OS Release 3.0 and NX-OS Release 4.1(1) or when
restrictions on oversubscription ratios are enabled, the port bandwidths are
allocated in equal proportions, regardless of port speed, so, the bandwidth
allocation for the same three ports mentioned in the example would be 1:1:1.
|