Lustre 1.6 Operations Manual

5.2.3 Downed Routers
There are two mechanisms to update the health status of a peer or a router:
■
■
LNET can actively check health status of all routers and mark them as dead or
alive automatically. By default, this is off. To enable it set auto_down and if
desired check_routers_before_use. This initial check may cause a pause
equal to router_ping_timeout at system startup, if there are dead routers in
the system.
When there is a communication error, all LNDs notify LNET that the peer (not
necessarily a router) is down. This mechanism is always on, and there is no
parameter to turn it off. However, if you set the LNET module parameter
auto_down to 0, LNET ignores all such peer-down notifications.
Several key differences in both mechanisms:
■ The router pinger only checks routers for their health, while LNDs notices all
dead peers, regardless of whether they are a router or not.
■ The router pinger actively checks the router health by sending pings, but LNDs
only notice a dead peer when there is network traffic going on.
■ The router pinger can bring a router from alive to dead or vice versa, but LNDs
can only bring a peer down.
Chapter 5 Configuring the Lustre Network 5-9