[j-nsp] Juniper M20 does not clear "show chassis alarms"/"show system alarms" although problem not present any more

[martin]

Hi,
sorry about cumbersome subject, at least it's informative :) However,
has anyone seen an issue with Juniper M20 where alarms("show chassis
alarms", "show system alarms") do not clear althought problem itself
is not present any more? I have a Juniper M20 router(JUNOS 9.4R4.5),
which has two AC PSU's(740-007311) installed. There were few short
power outages with one power feed(first one ~6min, second one ~6min
and third one ~30min) and finally :

Jan 19 07:21:11  M20 chassisd[1130]: CHASSISD_SNMP_TRAP6: SNMP trap
generated: Power Supply OK (jnxContentsContainerIndex 2,
jnxContentsL1Index 2, jnxContentsL2Index 0, jnxContentsL3Index 0,
jnxContentsDescr Power Supply B, jnxOperatingState/Temp 2)


"Power Supply A" is connected to other power-feed and was not affected
at all. As you can see, according to log, "Power Supply B" is fine.
"DC OK" light of "Power Supply B" is on and "show chassis environment
" output indicates as well, that "Power Supply B" is fine:

Class Item                           Status     Measurement
Power Power Supply A                 OK
      Power Supply B                 OK


According to Juniper
documentation(http://www.juniper.net/techpubs/software/junos/junos73/swcmdref73-basics-services/html/chassis-monitor18.html),
"You cannot clear the alarms for chassis components. Instead, you must
remedy the cause of the alarm. When a chassis alarm is lit, it
indicates that you are running the router in a manner that we do not
recommend."

However, I still see following output if I execute "show chassis
alarms" or "show system alarms":

user at M20> show chassis alarms
2 alarms currently active
Alarm time               Class  Description
2011-01-19 06:12:44 UTC  Major  Power Supply B not providing power
2011-01-19 06:13:41 UTC  Major  Power Supply B fan failed

user at M20>


I know, that rebooting the router would help, but what might cause
such issue? Has anybody encountered something similar?