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Cluster speeds

Sometimes you feel a cluster is slow.

Below are some benchmark results, so you can compare with what you are experiencing.

Please contact support when you find out that your favorite cluster is slower than expected.

What could cause such a slowdown?

When things are slow it is usually due to latency when many processes are accessing the same files and physical hard drives

Examples:

  • 2024-12-06: Castor is still holding some file systems for Bianca or a user that is running a lot of very short lived Perl jobs on Bianca, that are running too hard on Castor.

Starting an interactive session with two cores for one hour

In general:

  • It takes seconds if a free compute node is available
  • It takes minutes to start a new node
Date and time Cluster Command You waited for x seconds Complete time (secs)
2024-12-19 8:00 Bianca interactive -A sens2023036 -n 2 -t 1:00:00 518 (8:38) 548 (9:08)

You can expect longer times if:

How can I check that my project has used all of its resources?

Go to https://supr.naiss.se, click on your project and scroll down to 'Resources'.

There you can see how much of the computational resources you've used.

For example, below is an example project showing its resource usage:

An example project showing its resource usage

We can see that it uses zero percent of the computation resources of the Dardel HPC cluster, yet 116.4% of Rackham's. Starting an interactive job on Rackham may hence take longer.

Loading the R_packages/4.3.1 module

For a benchmark to solve a ticket, the following command was run in multiple settings:

time module load R_packages/4.3.1

From the three resulting times, the 'Real' time is used.

Here are some expected timings:

Project Setting Real loading time
Rackham SSH 0m0.758s
Bianca SSH 0m8.984s

Here are some unexpected timings:

Project Setting Real loading time
sens2023598 SSH 6m1.265s
sens2023598 Website 6m20.234s
sens2017625 SSH 6m4.584s
sens2017625 Website, interactive session 7m41.433s
sens2017625 SSH, interactive session 7m13.111s

Loading the RStudio/2023.12.1-402 module

Project Setting Real loading time
Bianca Website 2m3.184s