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Frank Schluenzen posted on 20. Oct. 2015 17:27h - last edited by Frank Schluenzen on 17. Jan. 2019 15:41h

Currently, EXFEL has a number of partitions:

The exfel partitions comprises various hardware platforms (see Maxwell Hardware for details) where different limits and constraints apply. Below are some details for the exfel partition in Maxwell, but it applies to any of the partitions likewise, just replace the partition exfel with your favorite partition. 

Support

Please consult with the documentation provided by the European XFEL.

For questions concerning access to any of the EXFEL partitions please contact it-support@xfel.eu.

For any more generic question or problem please send a message to maxwell.service@desy.de.

Have a look at the Maxwell pages, in particular on getting started, storage, running jobs.


Interactive Login Nodes

To login in to exfel part of the maxwell cluster you have different options depending on the hardware required. 

  • ssh max-display.desy.de: will connect you to one of the display nodes. FastX might your better choice. Please have a look at the Remote Login and the FastX documentation.
  • ssh max-exfl.desy.de:  will connect you to max-exfl001,14,15 (INTEL based part of the partition). It's a load-balanced alias. Use theses nodes to compile, test INTEL-tailored applications.
  • ssh max-wgs: will connect you to the generic login node. 
  • Unless you use hardware-specific compiler-flags, compilation and job-submission can done from any of the login nodes.
  • Please note: max-display.desy.de is directly accessible from outside. All other login nodes can only be reached by first connecting to bastion.desy.de. 

Login nodes are always shared resources sometimes used by a large number of concurrent users. Don't run compute or memory intense jobs on the login nodes, use a batch job instead!

The European XFEL Batch resource in Maxwell

As a first step login to one of the login nodes and check which Maxwell resources are available for your account using the my-partitions command:

my-partitions 
[@max-exfl ~]$ my-partitions 

      Partition   Access   Allowed groups                                                                               
---------------------------------------------------------------------------------------------------------------- 
            all      yes   all                                   <------- will be available if any of the resources below is "yes!
           cfel       no   cfel-wgs-users                
            cms       no   max-cms-uhh-users,max-cms-desy-users
       cms-desy       no   max-cms-desy-users            
        cms-uhh       no   max-cms-uhh-users             
           cssb       no   max-cssb-users                
      epyc-eval       no   all                           
          exfel      yes   exfel-wgs-users                       <------- look for this one as an EXFEL member
      exfel-spb       no   exfel-theory-users,school-users
       exfel-th       no   exfel-theory-users            
   exfel-theory       no   exfel-theory-users            
     exfel-wp72       no   exfel-theory-users            
        fspetra       no   max-fspetra-users             
           grid       no   max-grid-users                
           jhub       no   all                           
        maxwell      yes   maxwell-users,school-users            <------- might be granted if you have suitable applications
            p06       no   max-p06-users                 
         petra4       no   p4_sim                        
             ps       no   max-ps2-users            
            psx       no   max-psx2-users                
            uke       no   max-uke-users                 
           upex      yes   upex-users,school-users               <------- look for this one as an EXFEL user
     xfel-guest       no   max-xfel-guest-users,p4_sim   
        xfel-op       no   max-xfel-op-users             
       xfel-sim       no   max-xfel-sim-users


If it says "yes" for partition "exfel" (or upex etc) you are ready to go. If so you will also see  a "yes" at least for partition "all". If not: get in touch with it-support@xfel.eu! Let's assume that you've got the exfel-resource. The exfel-resource also offers great additional opportunities for remote login. It entitles you to use the max-display nodes to connect to the maxwell cluster via your browser or the fastx-client. 

Apart from that: If you have an application, which is started by a script called my-application, and doesn't require a GUI, you can simply submit the script as a batch-job:

sbatch 
[@max-exfl ~]$ sbatch --partition=exfel --time=12:00:00 --nodes=1 my-application
Submitted batch job 1613895

# the job might already be running
[@max-exfl ~]$ squeue -u $USER
             JOBID PARTITION     NAME     USER ST       TIME  NODES NODELIST(REASON)
           1614464     exfel   my-app     user  R       0:06      1 max-exfl052
# Status of the job                             R: running. PD: pending

This works for any application smart enough not to strictly require an X-environment, matlab, comsol, ansys, mathematica, idl and many others can be executed as batch jobs. To make it more convenient you can add the SLURM directives directly into the script:

sbatch script 
[@max-exfl ~]$ cat my-application
#!/bin/bash
#SBATCH --partition=exfel
#SBATCH --time=1-12:00:00      # request 1 day and 12 hours
#SBATCH --mail-type=END,FAIL   # send mail when the job has finished or failed
#SBATCH --nodes=1              # number of nodes
#SBATCH --output=%x-%N-%j.out  # per default slurm writes output to slurm-<jobid>.out. There are a number of options to customize the job 
[...] # the actual script.

The email-notification will be sent to <user-id>@mail.desy.de. That should always work, so you don't actually need to specify an email-address. If you do, please make sure it's a valid address. For further examples and instructions please read Running Jobs on Maxwell. 

If you think that it's much to complicated to write job-scripts or if you can't afford to invest the time to look into it: we are happy to assist. Please drop a message to maxwell.service@desy.de, we'll try our best. 

Running interactive batch jobs

If you absolutely need an interactive environment, X-windows features like a GUI, there are options to do that in the batch environment. For example:

salloc 
# request one node for 8 hours:
[@max-exfl ~]$ salloc --nodes=1 --time=08:00:00 --partition=all
salloc: Pending job allocation 1618422
salloc: job 1618422 queued and waiting for resources
salloc: job 1618422 has been allocated resources
salloc: Granted job allocation 1618422
salloc: Waiting for resource configuration
salloc: Nodes max-exfl022 are ready for job


# now you got a node allocated. So you can ssh into the node
[@max-exfl ~]$ ssh max-exfl022 
[@max-exfl022 ~]$ # run your application!
[@max-exfl022 ~]$ exit # this terminates the ssh session, it does NOT terminate the allocation
logout
Connection to max-exfl022 closed.
[@max-exfl ~]$ exit
exit
salloc: Relinquishing job allocation 1618422
# now your allocation is finished. If in doubt use squeue -u $USER or sview to check for running sessions!

There are a few things to consider:

  • Interactive jobs with salloc easily get forgotten, leaving precious resources idle. We do accounting and monitoring! 
  • Keep the time short: there is hardly a good reason to run an interactive jobs for more than the working hours. Use a batch job instead.
  • Terminate allocations as soon as the job is done!

Other Maxwell Resources

Being member of EXFEL and maybe having access to the exfel partition doesn't need to be the end of the story. If you have parallelized applications suitable for the Maxwell cluster you can apply for the Maxwell resource like everyone else on campus. Please send a message to maxwell.service@desy.de briefly explaining your use case. Being also a user of the European XFEL you might also have access to the UPEX partition. You can easily distribute your job over the partitions:

multiple partitions 
[@max-exfl ~]$ cat my-application
#!/bin/bash
#SBATCH --partition=exfel,maxwell,upex,all
#SBATCH --time=1-12:00:00      # request 1 day and 12 hours
#SBATCH --mail-type=END,FAIL   # send mail when the job has finished or failed
#SBATCH --nodes=1              # number of nodes
#SBATCH --output=%x-%N-%j.out  # per default slurm writes output to slurm-<jobid>.out. There are a number of options to customize the job 
[...] # the actual script.

The partition will be selected from exfel OR maxwell OR upex OR all starting with the highest priority partition. So your job will run on the exfel partition if nodes are available, on the maxwell partition if nodes are available and finally on the all partition if none of the other partitions specified have free nodes. Keep in mind that you should however select the partition according to the type of work you are doing. And a job can never combine nodes from different partitions, so check the limits applying to partitions.

To check availability of nodes and characteristics use sinfo (https://slurm.schedmd.com/sinfo.html)

sinfo
[@max-display001 ~]$ sinfo -p upex -o "%10P %.6D %8c %8L %12l %8m %30f %N"
PARTITION   NODES CPUS     DEFAULTT TIMELIMIT    MEMORY   AVAIL_FEATURES                 NODELIST
upex           80 80       1:00:00  14-00:00:00  512      INTEL,V4,E5-2698               max-exfl[020-099]
upex            2 40       1:00:00  14-00:00:00  256      INTEL,V4,GPU,P100,E5-2640      max-exflg[006-007]
upex            4 40       1:00:00  14-00:00:00  256      INTEL,V4,E5-2640               max-exfl[016-019]


[@max-display001 ~]$ sinfo -p upex -o "%10P %.6D %10s"
PARTITION   NODES JOB_SIZE  
upex           86 1-16
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