Sněhurka

Karlínský výpočetní cluster

Sněhurka cluster relocation to Troja HPC facility

2026-06-02 · Downtime, News, Novinky

Most of the machines of the Sněhurka computing cluster in Karlín was moved to a new server room in Troja and was integrated into the Chiméra cluster there. Users can now take full advantage of the relocated cluster. We ask users to move their cluster data from Karlín to Troja by September 30, 2026.

Details of the relocation are provided below:

Transfer of cluster data from Karlín to Troja

The current situation is as follows:

  1. The data for the Karlín cluster (both cluster "home" [/usr/users/login] and "work" [/usr/work/login]) is now stored on an old disk array (pole2018).
    • We purchased the disk array in 2018 (i.e., 8 years ago), and it is no longer under warranty.
    • The disk array has two controllers (components that manage the operation of the entire array) – one serves as a backup for the other. However, one controller is no longer functional, so while the array continues to operate, we no longer have a "backup" controller.
    • The data in cluster "home" is backed up (usually every night), but the data in "work" is not backed up.
  2. We will need space for users who will continue to use GPU nodes g1–g6 (which will remain in Karlín).
  3. The storage capacity of the Troja cluster has recently been significantly increased, so there is now sufficient space available.

In light of the above:

  1. We ask Karlín users who do not use the Karlín GPU nodes (g1–g6) to move their cluster data from Karlín to Troja (not just "copy", but actually "move" – to free up space in Karlín) by the end of the academic year (i.e., by September 30, 2026). After that, only the cluster data of GPU nodes (g1–g6) users should remain in Karlín (on the pole2018 disk array).
    • Instructions on how to transfer data to the Chimera cluster are available on the Chimera (usefull notes for migration) webpage.
    • We ask users who wish to continue performing computations on the g1-g6 GPU nodes (i.e., whose cluster data will remain in Karlín) to contact me (so we are aware of them) at the email address martin.trcka@matfyz.cuni.cz.
  2. We then plan to move the remaining data (i.e., data from users of g1–g6) to a Karlín storage location that is better protected against failure (than the pole2018 disk array). Details are yet to be determined.

Relocation schedule

The dates listed are tentative and subject to change depending on how the situation develops.

What is the Chimera cluster?

The Chimera cluster is an HPC (high-performance cluster) currently located in the "old" server room in Troja (and will also be moved to the "new" server room in Troja). More detailed information about the cluster can be found on the website: https://www.mff.cuni.cz/en/hpc-cluster/ (login via CAS is required).

The cluster website also has a section dedicated to Introductory training (June 2022), which includes a link to slides [pptx, 17 slides, 9 MB] (the slides don't contain all the material covered in the hands-on session) and a recording of the entire training session [mp4, 2 h 25 min, 1.7 GB].

Where and why is the Karlín cluster moving?

There are several different computing clusters in various locations at the Faculty of Mathematics and Physics. A new server room is currently being completed in Troja, to which clusters from other locations will gradually be moved and unified under central administration.

Advantages of consolidating and unifying computing clusters:

How will the sharing of unused computing capacity work?

The sharing of computing nodes will work on the following principle:

  1. Those who provided/financed the computing nodes (schools, departments, groups) will have priority access to these nodes (in the form of higher priority computing queues).
  2. However, when the nodes are not in use, anyone else will be able to use them. Each node in the cluster will be part of a queue that will have the lowest priority but will be of the FFA (free for all) type.

Which Karlín machines will be moved to Troja?

The following will be moved to Troja:

In addition, two new computing CPU nodes purchased from the UNCE project (prof. J. Málek) will be delivered directly to Troja (expected delivery date is in the first half of 2026).

The following will not be moved to Troja:

What is the RSE (Research Software Engineering) group?

RSE group is a university group of people (currently approx. 3-4 employees) who can help users with the use of the cluster. It serves as an interface between the latest technologies and the academic environment.

The main goal of RSE is to reduce barriers to computing resources, for example:

Website: https://rse.cuni.cz/

Information about RSE was also presented at Jaroslav Hron's training course.