3
–
InfiniBand
®
Cluster Setup and Administration
Changing the MTU Size
3-20
IB0054606-02 A
Changing the MTU Size
The Maximum Transfer Unit (MTU) size enabled by the IB HCA and set by the
driver is 4KB. To see the current MTU size, and the maximum supported by the
adapter, type the command:
$ ibv_devinfo
If the switches are set at 2K MTU size, then the HCA will automatically use this as
the active MTU size, there is no need to change any file on the hosts.
To ensure that the driver on this host uses 2K MTU, add the following options line
(as a root user) in to the configuration file:
options ib_qib ibmtu=4
shows the value of each ibmtu number designation.
The following is a list of the configuration file locations for each OS:
For RHEL 5.x use file:
/etc/modprobe.conf
For SLES 10 or 11 use file:
/etc/modprobe.conf.local
For RHEL 6.x use file:
/etc/modprobe.d/ib_qib.conf
Restart the driver as described in
.
Table 3-1. ibmtu Values
Number Designation
Value in Bytes
1
256
2
512
3
1024
4
2048
5
4096
Summary of Contents for OFED+ Host
Page 1: ...IB0054606 02 A OFED Host Software Release 1 5 4 User Guide...
Page 14: ...xiv IB0054606 02 A OFED Host Software Release 1 5 4 User Guide...
Page 22: ...1 Introduction Interoperability 1 4 IB0054606 02 A...
Page 96: ...4 Running MPI on QLogic Adapters Debugging MPI Programs 4 24 IB0054606 02 A...
Page 140: ...6 SHMEM Description and Configuration SHMEM Benchmark Programs 6 32 IB0054606 02 A...
Page 148: ...8 Dispersive Routing 8 4 IB0054606 02 A...
Page 164: ...9 gPXE HTTP Boot Setup 9 16 IB0054606 02 A...
Page 176: ...A Benchmark Programs Benchmark 3 Messaging Rate Microbenchmarks A 12 IB0054606 02 A...
Page 202: ...B SRP Configuration OFED SRP Configuration B 26 IB0054606 02 A Notes...
Page 206: ...C Integration with a Batch Queuing System Clean up PSM Shared Memory Files C 4 IB0054606 02 A...
Page 238: ...E ULP Troubleshooting Troubleshooting SRP Issues E 20 IB0054606 02 A...
Page 242: ...F Write Combining Verify Write Combining is Working F 4 IB0054606 02 A Notes...
Page 280: ...G Commands and Files Summary of Configuration Files G 38 IB0054606 02 A...
Page 283: ......