[torqueusers] sporadic scp failures

Joshua Bernstein jbernstein at penguincomputing.com
Wed Feb 17 11:45:55 MST 2010


	Have you looked through the pbs_mom log files, or even /var/log/messages on the 
headnode? You might be running into a situation where either pbs_mom or sshd (on 
the headnode) is running out of open file descriptors. If you're using bash 
shell, you have a look at the maximum number of open files per process using:

$ ulimit -n

Generally this number is set to 1024 by default, but if you have a large 
cluster, and the headnode is rather busy, SSHD may not be able to fork() in 
order to receive the incoming SCP connection.

-Joshua Bernstein
Senior Software Engineer
Penguin Computing

Jeff Anderson-Lee wrote:
> I'm getting sporadic failures when it tries to copy the results .ER and 
> .OU files back.  It is not 100% of the time, nor is is 100% consistent 
> on which hosts have problems.  Sometimes the same host will succeed for 
> one or both files and sometimes it will fail for both.
> I'm wondering if this might have something to do with too many scp 
> requests showing up simultaneously and some sort of rate-limiting 
> happening.  Any suggestions on where I might look?  What I might tweak?  
> Is there some way to increase the default socket backlog, or that used 
> by inetd/sshd?
> Thanks.
> Jeff Anderson-Lee
>> PBS Job Id: 958.XXX.berkeley.edu
>> Job Name:   STDIN
>> Exec host:  s103/11
>> An error has occurred processing your job, see below.
>> Post job file processing error; job 958.XXX.berkeley.edu on host s103/11
>> Unable to copy file /var/spool/torque/spool/958.XXX.berkeley.edu.OU to 
>> jonah at XXX.berkeley.edu:/home/cs/jonah/STDIN.o958
>> *** error from copy
>> ssh_exchange_identification: Connection closed by remote host
>> lost connection
>> *** end error output
>> Output retained on that host in: 
>> /var/spool/torque/undelivered/958.XXX.berkeley.edu.OU
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