Agenda

This version (2024/10/24 10:28) is a draft.
Approvals: 0/1

User accounts and passwords are NOT identical to your MUL account
User name = first letter of given name + full surname
example: Erich Mustermann … emustermann
Connections limited to MUL network
- use MUL VPN if necessary
Use a terminal program: xterm, putty, terminal, …

ssh -X <username>@mul-hpc-81a.unileoben.ac.at
ssh -X <username>@mul-hpc-81b.unileoben.ac.at

OS X

If, e.g., you have an US keyboard layout, you may have to include the following lines have in your <html></html>.bashrc file<html></html> on the login node in order to be able to submit jobs:

export LC_CTYPE=en_US.UTF-8
export LC_ALL=en_US.UTF-8

Alternatively, you can change the same directly on your Mac in

<html></html> Terminal ➠ Preferences ➠ Profiles ➠ Advanced ➠ International <html></html>

Uncheck the option “Set locale environment variables on startup” and restart the terminal.

We have 3 filesystems for users:

/home … essentially only for config files
- NOT for data
- NOT for calculations
- NOT for compiling codes
/calc … for data (also longer time) and for running calculations
/scratch … fast filesystem for running calculations only

The filesystems are mounted:

via Infiniband on login nodes and compute nodes c1-xx, c2-xx
via Ethernet on all other nodes (c3-xx, c4-xx, c5-xx)

We use ZFS filesystems with these RAID Levels and disk types:

RAID10 on SSDs for /home and /scratch
RAID(Z3)0 on HDDs for /calc
- this is similar to RAID60 but with 3 redundancy disks

home directories are located in /home
mounted via NFS from fileserver f1
For performance reasons /home is separate from /calc
- even if /calc is heavily loaded, /home should still be responsive
- … important for interactive work
quota per user: 10 GB
- /home is only for config files
- not for compilation of codes (use /calc for this)

The directory structure is:

/home/<username>

By default permission are set to 0700:

rwx------

Directories and files are only accessible by user,
- no access for group
- no access for others.
The settings can be changed by the user who owns the directory.

located in /calc and mounted via NFS from fileserver f2
directory structure is the same as for /home:

/calc/<username>

permissions are the same as for /home

rwx------

this is the place for
- calculations
- compiling codes
- data
calculations
- especially for calculations with low IO requirements
- on our previous clusters > 90% of calculations were not IO intensive

/calc has a size of approx. 200 TB
the group quota for /calc depends on your cluster share
- e.g. if you contributed 20% of the money you can use 20% of 200 TB = 40 TB
every group can have an arbitrary number of users therefore there is no uniform user quota

mounted via NFS from fileserver f1
directory structure is the same as for /home or /calc:

/scratch/<username>

permissions are the same as for /home or /calc

rwx------

this is the place for IO heavy calculations
this can be used for software that supports a scratch directory
- e.g. option scratch=/scratch/username of Abaqus
this is NOT the place for storing files for a longer time
- there will be some policy for automatic deletion of data
this is also not the place for jobs with almost no IO
- these would gain nothing
- but would only waste space

/scratch has a size of approx. 16 TB
there is no need for a quota if you use /scratch like intended:
- copy files for a job from /calc to /scratch
- run job
- copy results of job back to /calc
- delete job data immediately from /scratch
the best method is to do the copying and removing in your job script

example (non-working skeleton):

#!/bin/bash
#SBATCH ... see slurm slides ...

[...]
CALC=/home/username/someproject
MYTMP=$(mktemp -p /scratch/username -d)

cp -a $CALC $MYTMP
cd $MYTMP

# run the software here

cp -a $MYTMP/.  $CALC/.
rm -rf $MYTMP

copy data to cluster:

[...]$ scp <filename> <username>@<servername>.unileoben.ac.at:~/

The servername can be one of these:

mul-hpc-81a , mul-hpc-81b
- the 2 login nodes provide slow access to all filesystems
mul-hpc-81-fs1
- fileserver 1 is fastest for /home and /scratch
mul-hpc-81-fs2
- fileserver 2 is fastest for /calc

reduces amount of data sent over the network
- “quick check” algorithm ➠ only changes sent
rsync options: ➠ rsync -av
- recursive, copies symlinks, preserves permissions, modification times, group, special files, owner
Alternatively, data can be copied using, e.g., either <html></html> ➠ FileZilla <html></html> or <html></html> ➠ winscp <html></html>

Backup Policy: <html></html> no backup of user data ➠ backup is solely the responsibility of each user <html></html>

write an e-mail to the MUL-HPC support address
- with CC to head of your chair
Address: mul-hpc-support@unileoben.ac.at

jobs are scheduled in a way that ensures a fair usage of the resources (mostly CPU cores)
- according to predefined percentages
there is no static allocation of resources
- this would be inflexible and bad for overall utilization
instead resources are scheduled dynamically

see Background information slides for more technical details

write an e-mail to the MUL-HPC support address
Address: mul-hpc-support@unileoben.ac.at

there is a hierarchy of scratch directories
- /dev/shm … RAM disk which uses a maximum of 1/2 of the memory
- /tmp … local /tmp directory of the node
- /scratch/username … global (on fileserver) scratch directory
you can an use a script like the one shown above to copy/remove data
n.b.: everything you copy into /dev/shm reduces the available memory

Agenda

Introduction to Working on the MUL Cluster

General remarks

Login

Linux and OS X

OS X

Filesystems

Home directories

Home directories

/calc directories

purpose of /calc

/calc quota

/scratch directories

purpose of /scratch

/scratch quota

using /scratch in job script

Tranferring data

copy data to cluster:

Tranferring data

backup of data ➠ rsync

Policies

How to get an account

Policies

Fair share usage

Policies

Getting help

Scratch directories