Hortense @ HPC-UGent


This documentation is still being completed.

More information and details will be added in the coming days.

In case of questions, please contact compute@vscentrum.be.

General information

Hortense is the 3rd VSC Tier-1 cluster, following muk (hosted by HPC-UGent, 2012-2016) and BrENIAC (hosted by HPC-Leuven, 2016-2022).

The first phase of Hortense is also named dodrio.

It is available since 2021, is hosted by Ghent University, and maintained and supported by the HPC-UGent team.

Hardware details

Hortense currently consists of 3+1 partitions:

  • dodrio/cpu_rome: main partition:
    • 294 workernodes, each with:
      • 2x 64-core AMD Epyc 7H12 CPU 2.6 GHz (128 cores per node)

      • 256 GiB RAM (~2GB/core), no swap

  • dodrio/cpu_rome_512: large-memory partition:
    • 42 workernodes, each with:
      • 2x 64-core AMD Epyc 7H12 CPU 2.6 GHz (128 cores per node)

      • 512 GiB RAM (~4GB/core), no swap

  • dodrio/gpu_rome_a100: GPU partition:
    • 20 workernodes, each with:
      • 2x 24-core AMD Epyc 7402 CPU 2.8 GHz (48 cores per node)

      • 4x NVIDIA A100-SXM4 (40 GB GPU memory), NVLink3

      • 256 GiB RAM (~5GB/CPU core), no swap

  • dodrio/cpu_rome_all: combination of cpu_rome and cpu_rome_512

Shared infrastructure:

  • storage: 3 PB shared scratch storage, based on Lustre (see $VSC_SCRATCH_PROJECTS_BASE);

  • interconnect: InfiniBand HDR-100 (~12.5GB/sec), 2:1 fat tree topology

    • for the GPU partition specifically: dual HDR-100 Infiniband


A high-level overview of the cluster can be obtained by running the pbsmon command.

Getting access

The Hortense VSC Tier-1 cluster can only be used by people with an active Tier-1 compute project.

See https://www.vscentrum.be/compute for more information on requesting access.

To access the Tier-1 Hortense cluster, use SSH to connect to the dedicated login node with your VSC account:

  • from the public internet, use tier1.hpc.ugent.be

  • from within the VSC network, use tier1.gent.vsc

More general information about SSH login is available at Access and data transfer.


There is currently only one small login node (16 cores, 64GB RAM) available.

Please only use the login node as an access portal!

For resource-intensive tasks, like software compilation, testing job scripts, etc., please use an interactive job.


The login node of the Tier-1 Hortense cluster is currently only accessible via SSH.

Alternative methods (using NX, a web portal) will be available soon.

Managing project members

Managing members of a project can be done by the Principal Investigator (PI) and group moderators of the project via the VSC accountpage, as follows:

  • Go to the Edit Group tab;

  • Select the group that corresponds to the project you want to manage. For projects on the Tier-1 cluster Hortense, the group names all start with “gpr_compute_”.

  • Click the Edit button once the group that corresponds to your Tier-1 project is selected.

  • Change group membership via the Manage members section on the next page:

    • To remove a project member:, click the x next to the VSC account that was invited in the Members subsection.

    • To invite someone to join the project: click the box in the Invite users subsection, add select a VSC account ID to send a join invitation to. Note that you can filter the accounts to select by (partially) typing the name of the VSC account.

    • To cancel a pending invitation: use the x next to the VSC account that was invited.

    • To promote a project member to group moderator: click the box in the Moderators subsection and select their VSC account ID.

  • Click Update to apply the changes you made.

Keep in mind that:

  • Group join invitations need to be accepted first before the VSC account is added to the group.

  • It can take a while (about one hour) before any changes in group membership are reflected on the system itself.

Sending a request to join a project

You can submit a request to join a Tier-1 project to the moderators of the corresponding group via the VSC accountpage, as follows:

  • Go to the New/Join Group tab;

  • Select the group that corresponds to the project you want to join in the Join group section. For projects on the Tier-1 cluster Hortense, the group names all start with “gpr_compute_”.

  • In the Message field, add a short message that will be included in the join request that will be sent to the group moderators. Make it clear who you are, and why you want to join the project.

  • Click Submit to send the group join request.

Keep in mind that:

  • Your request needs to be approved by one of the group moderators before your VSC account is added to the group.

  • It can take a while (about one hour) before any changes in group membership are reflected on the system itself.

System-specific aspects

Storage quota usage

  • You can check personal and project storage quota usage by running the my_dodrio_quota command.

  • If you want to check storage quota for specific projects, or for projects that are not listed automatically, use the -p option.

  • For a list of all options, run my_dodrio_quota -h.

(more information soon)


Operating system

Both login nodes and workernodes in Hortense use Red Hat Enterprise Linux 8 (RHEL8) as operating system.

Resource manager

Slurm is used as resource manager and job scheduler.

A Torque frontend (implemented by the VSC support team in the jobcli Python library) that provides wrapper commands for the familiar Torque commands qsub, qstat, qdel, etc. is available.

We strongly recommend using the Torque frontend for submitting and managing your jobs!

Commands for job submission & management

  • qsub: submit job script(s);

  • qsub -I: submit an interactive job;

  • qstat: get a list of all currently queued and running jobs;

  • qdel: delete jobs;

  • qalter: change submitted jobs;

  • qhold: put jobs on hold;

  • qrls: release held jobs;

General command options

The following options are supported for each of the Torque frontend commands listed above:

  • --help: show supported command options;

  • --version: print version information for jobcli and Slurm;

  • --debug: show detailed information about how the command is executed in the backend (Slurm);

    • for qsub, this includes the contents of the job script like it will be submitted;

  • --dryrun: see how a command would be executed, without actually executing the corresponding backend commands;

#PBS header lines in job script

Resource specifications and job metadata for a job can be specified via #PBS lines in the header of the job script.

See qsub --help for a list of supported options.

For example:

#PBS -l nodes=1:ppn=64
#PBS -l walltime=10:00:00

Specifying a project

When submitting jobs to Hortense, it is required that you specify which project credits you want to use (see also Getting access).


The terminology used by the Slurm backend is “accounts”, while we usually refer to projects.

Specifying a project can be done in the qsub command, using the -A option:

qsub -A example script.sh

Or via a #PBS header line in your job script:

#PBS -A example

Another option is to define the $SLURM_ACCOUNT environment variable (for example in your $HOME/.bashrc startup script on Hortense):

export SLURM_ACCOUNT='example'

If you’ve specified an incorrect project name through one of the mechanisms mentioned above, the qsub command will produce a helpful error that mentions the names of the projects you currently have access to:

$ qsub -A wrong_project script.sh
ERROR: Specified account 'wrong_project' is not valid (valid account(s): valid_project_1, valid_project_2)


Be careful when you are a member of multiple Tier-1 Hortense projects, make sure that you always specify the correct project to avoid accidentally exhausting the credits of a project unintendedly.

Submitting to a specific cluster partition

To submit to a specific partition, swap to the corresponding cluster/dodrio module before running the qsub command.

For example, to submit a GPU job:

module swap cluster/dodrio/gpu_rome_a100
qsub job_script.sh

A list of available partitions can be obtained using module avail cluster/dodrio.

To check the currently active partition, use module list cluster.

Limitations for jobs

Maximum walltime

The maximum walltime that jobs can request is 3 days (72 hours): -l walltime=72:0:0.

Jobs that request more walltime will be refused by the resource manager at submission time (”Requested time limit is invalid”).

Scientific software

A central software stack with a rich set of scientific libraries, tools, and applications is available via the module command, and was installed using EasyBuild.

Use module avail to see which software versions are available, and load one or more modules via the module load command to start using them.

If software that you require is missing, please submit a software installation request via https://www.ugent.be/hpc/en/support/software-installation-request .

Access to licensed software

For licensed software, you may need to be a member of a specific group of users in order to access the available central software installations.

If not, you will see an error message as shown below when trying to load the module for the licensed software you would like to use:

You are not part of 'gli_example' group of users that have access to this software.
Creating a software license group

If a license to use the software on the VSC Tier-1 cluster Hortense hosted by Ghent University is available, the Principal Investigator (PI) of the Tier-1 project should take the following steps to let project members use the license software:

  1. Create a dedicated user group that only contains the VSC accounts that should be able to access the licensed software. This can be done via the VSC accountpage:

  • Visit https://account.vscentrum.be/django/group/new .

  • Use the “Create new group” section at the bottom of the page.

  • Pick a group name that starts with ‘xli_’, where ‘x’ corresponds to the first letter of the VSC site that your VSC account is connected with. Note that this letter is prepend automatically to the specified group name! The ‘li_’ infix in the group name allows us to easily discriminate groups that are used to manage access to software licenses.

  • You are free to choose the last part of the group name after ‘xli_’, but please keep these guidelines into account:

    • The group name should indicate to which software is is related.

    • The group name should indicate for which research group, or company, etc. it is for.

  • For example: ‘gli_soft_grp’ would be a good group name for a licensed software application named ‘soft’, and a (UGent) research group named ‘grp’.

  • The VSC account used to create the group will automatically be a moderator of that group, and add additional group members (and moderators), and approve join requests, via https://account.vscentrum.be/django/group/edit .

  • Note that all members of this group should be allowed to use the licensed software! It is the responsibility of the group moderators to ensure this is indeed (and remains to be) the case. The Tier-1 support team will not intervene in the management of this software license user group.

  1. Contact compute@vscentrum.be to request that the users of this group should have access to the licensed software, and include the following information:

    • The name of the licensed software that the request relates to.

    • A list of names of centrally installed modules that group members should be able to use.

    • The name of the software license user group.

    • To which Tier-1 project your request relates to.

    • A document that clearly shows that you have a license for the software, or a reference to your project application that includes this already.

    • Clearly mention that your request relates to the Hortense Tier-1 cluster in the subject of your message.

Managing a software license group

To add one or more VSC accounts to an existing software license group:

Likewise, a group moderator can manage the software license group via https://account.vscentrum.be/django/group/edit, by:

  • Promoting a group member to group moderator.

  • Removing existing group members (or moderators).


Take into account that it takes a while (up to 1 hour) before any changes to a user group that were made in the VSC accountpage are active on the Tier-1 system itself.

If an existing software license group should no longer have access to central installations of installed software, please contact compute@vscentrum.be.


Getting help

For questions and problems related to Tier-1 Hortense, please contact the central support address for Tier-1 compute: compute@vscentrum.be.