Most of the machines in the Sněhurka computing cluster in Karlín will be moved to a new server room in Troja and integrated into the Chiméra cluster there. We plan to move the cluster in the first half of March 2026.
This change will affect Sněhurka cluster users in two ways:
- During the move (expected to take a few days), the relevant Sněhurka cluster computing nodes will be unavailable. Chiméra cluster nodes will be available during this time.
- The control and rules of the Chiméra cluster differ in some respects from those of the Sněhurka cluster. In January 2026, Jaroslav Hron will conduct an online training session to explain these changes. We will send out invitations once the training date has been set.
Details of the relocation are provided below:
- Relocation schedule
- What is the Chimera cluster?
- Where and why is the Karlín cluster moving?
- How will the sharing of unused computing capacity work?
- Which Karlín machines will be moved to Troja?
Relocation schedule
The dates listed are tentative and subject to change depending on how the situation develops.
- Probably during the week of January 12-16, 2026: cluster training (J. Hron, RSE)
- Mid-February: completion of the new server room in Troja (if completion is delayed, the relocation dates will also have to be postponed)
- Probably February 24, 2026 (Tuesday): first wave of relocation = transfer of the Troja Chiméra cluster from the old server room to the new one (i.e., Chiméra cluster downtime – a few days)
- Probably March 10, 2026 (Tuesday): second wave of relocation = transfer of the Karlín Sněhurka cluster (and also servers from other locations, e.g., Malá Strana, Jinonice, Ovocný trh) to the new server room in Troja (i.e., Sněhurka cluster downtime – a few days); the actual downtime of the Sněhurka cluster will begin about half a day earlier (i.e., on Monday at 12:00 p.m.) due to necessary preparations
- Probably until June 30, 2026 (at least 3 months): time for users to move their data from the Sněhurka cluster to Troja
What is the Chimera cluster?
The Chimera HPC (high-performance cluster) is 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/
The cluster website also has a section dedicated to Introductory training (June 2022), which includes a link to slides and a recording of the entire training session.
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:
- More efficient use of technical resources:
- Sharing unused computing capacity
- Space, electricity, cooling, data network, data storage
- More efficient use of human resources:
- Hardware and software management, easier sharing of know-how
- It is difficult for users to work with multiple different clusters (different accounts, controls, settings, rules)
- The unified cluster will have support that local clusters do not have:
- In the first half of 2026, the cluster will be reinforced with new "shared" computing nodes (CPU and GPU) and other equipment worth a total of approximately CZK 24 million
- Users will receive assistance in using the cluster (Research Software Engineering group)
- The university will contribute financially to the operation of the cluster
How will the sharing of unused computing capacity work?
The sharing of computing nodes will work on the following principle:
- 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).
- 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:
- all CPU nodes (r31–r50)
- InfiniBand 100 Gb switch
In addition, two new "Karlín" computing CPU nodes purchased from the UNCE project will be delivered directly to Troja (expected delivery date is in the first half of 2026).
The following will not be moved to Troja:
- all GPU nodes (g1–g6), because their form factor (dimensions and other physical characteristics, including cooling requirements) is not suitable for mounting in server room rack stands
