Troubleshooting guide

If the GM tree is not mounted by NFS, copy the 3 files created by this command

(static.map, static.routes, and static.hosts) to each <install_path>/sbin/ directory

on each host.

For auto-mapping at boot time, add the following command to the boot scripts of

the host (scripts in /etc/init.d or /etc/rc.d/init.d).

cd <install_path>/sbin/

su root

./file_mapper ../etc/gm/file.args

“High Availability” Mapping is the third way in which the GM mapper may be used.

This method is for users who have a need for High Availability (HA) in an aggressive

computing environment. The command for this method of running the GM mapper is:

cd <install_path>/sbin/

su root

./mapper ../etc/gm/active.args &

“High Availability” Mapping will continuously run the GM mapper in the background

to detect and add any new hosts or remove any non-responding hosts, to detect any

change of topology (change of slots in the switch, change of innerswitch topology), and

to periodically update the routing tables of the Myrinet cards (by default, every 30

seconds).

You should note that this HA mapping method is slightly intrusive. Since the GM

mapper uses unreliable messages that may be dropped in case of heavy contention, this

method of mapping can lead to hosts involved in a long computation being marked as

“non-responding” and removed from the routing tables because they are unreachable.

For the majority of users, the "map_once" GM-1 mapping method is sufficient. For the

users with more production-level constraints, the "static mapping" is the recommended

method. For fault-tolerant GM applications, the third method provides the best

alternative.

4. Enabling IP over Myrinet (Ethernet emulation) (OPTIONAL)

If you wish to run IP over Myrinet (ethernet emulation), the Linux command to enable IP

over GM is as follows:

/sbin/ifconfig myri0 <ip_address> up

where you must replace myri0 with the appropriate name (myri1, myri2, etc.) if you have

more than one Myrinet NIC per host.

To obtain good IP performance over Myrinet, we recommend the use of Linux 2.4. Note

that GM-2 yields better IP performance over Myrinet than GM-1.