DeskI Processing Server disabled automatically in cluster XIR3 environment

hi,

I have a problem theses days.

BOE Version: XI3.0

There is a cluster environment with 8 Windows machines.

Restart the machines every morning with the command "shutdown -r -m
rhnlpiwa7 -f"

by turn every 25 minutes.

(machine: rhnlpiwa1~7)

eg. restart rhnlpiwa1 9:00 am

rhnlpiwa2 9:25 am

rhnlpiwa3 9:50 am

rhnlpiwa4 10:15 am

......

The problem is that there will be 1~3 Desktop Intelligence Processing Server disabled automatically.

And when restart the disabled DeskI Processing Servers, they will be enabled.

I read the log file and found that the disabled rhnlpiwa3.Desktop Intelligence Processing Server

registered on rhnlpiwa7.Central Management Server:6400.

Could anyone tell me how to solve the problem?

And why are the servers disabled?

Thanks very much.