Migration guide¶

The NAISS systems Tetralith, Alvis and Dardel will be retired.

Users and projects from Tetralith, Alvis and Dardel will be migrated to Arrhenius.

For Tetralith and Alvis users and projects this process will happen during summer 2026, for Dardel later autumn 2026.

The main steps of migrating to Arrhenius are:

• Getting a storage and compute allocation on Arrhenius for the project
• Getting a personal login account on Arrhenius
• Testing your applications on Arrhenius
• Moving data from the project storage directory to Arrhenius
• Moving data from user's home directories to Arrhenius

These steps will be broadly similar no matter which system you are migrating from, but there will be minor differences. Please read the "When moving from XXXX" sections below carefully for the system you are migrating from.

When will the migration happen?¶

The HPC part of Arrhenius (CPU, GPU and HPC storage) became available to users (existing Tetralith and Alvis project as well as new Arrhenius projects) on 2026-06-01.

Tetralith and Alvis are scheduled to be shut down (as NAISS resources) on 2026-09-30. The shutdown date for Dardel is 2026-12-31. Dardel projects will get access to Arrhenius during 2026H2.

The size of Tetralith and Alvis (number of available compute nodes) will be reduced. Tentative start dates: 2026-06-10 for Tetralith and 2026-07-01 for Alvis.

We recommend that you start testing Arrhenius as soon as you get access and move your work to Arrhenius as soon as possible.

Arrhenius will not share any file systems with Tetralith, Dardel and Alvis. You will not be able to directly access files from project storage or home directories on Tetralith from Arrhenius and vice versa.

Getting a storage and compute allocation on Arrhenius for your project¶

Projects with an allocation on Tetralith or Alvis that ends after June 1^st 2026 automatically got an allocation on Arrhenius for the remaining time of the project.

Existing Dardel projects with an end date after the planned Dardel shutdown date will also get projects on Arrhenius automatically later on.

The size of the new allocation is scaled so that all projects from Tetralith, Alvis and Dardel (the systems that will be replaced by Arrhenius) will fit into the HPC part (there are also two much smaller sensitive data and persistent compute parts) of Arrhenius.

Removing "cold" data from Alvis¶

See the Alvis data migration page

Removing "cold" data from Tetralith¶

On Tetralith, you can use the command storagereport to get an overview of how much "cold" data the project has (data that has not been accessed in a long time). Such data should not be stored on Tetralith or Arrhenius, and you will likely need to remove some of it before your data will fit into your storage allocation on Arrhenius.

The PI or proxy for the PI can request assistance from NSC Support to access or remove user's data in the project storage directory.

Getting a personal login account on Arrhenius¶

All users who will be using Arrhenius need to request a login account in SUPR. When you do this, you will get to choose your username, password, setup two-factor authentication, etc.

This is described in more detail near the top of this page.

Testing your applications on Arrhenius¶

We recommend that projects login and get familiar with Arrhenius as soon as they get access. This includes reading the documentation, making sure you can login, transfer files, check if the applications you need are already installed, etc.

We recommend that you then copy or move a small amount of data (see "Transfer of files" on this page) to Arrhenius and run some test jobs. If you run into problems, do not hesitate to contact NAISS Support.

When you are happy with how Arrhenius works, it is time to move your data and start using Arrhenius instead of the previous system.

When migrating from Alvis¶

See the Alvis data migration page

When migrating from Tetralith¶

There will be a period of time where both Tetralith and Arrhenius are available (2026-06-01 to 2026-09-30). The project PI can decide when during this period the project will move to Arrhenius.

This overlap period is intended to make the move to Arrhenius easier, not to provide extra computing resources. We expect that projects that have migrated to Arrhenius will stop using Tetralith. The size of Tetralith will be gradually reduced during the overlap period, both to save on operating costs and to encourage migration.

NAISS recommends that projects move as early as possible. The main reason is that the later you move, the less time is available to fix any problems you might encounter on Arrhenius until you can no longer use Tetralith.

Moving data from the project storage directory to Arrhenius¶

When migrating from Alvis¶

See the Alvis data migration page

When migrating from Tetralith¶

When the project is ready to move, the project PI needs to decide what data from the project storage directory (e.g /proj/DIRECTORYNAME) should be moved to Arrhenius and when.

NAISS strongly recommends that projects request that NAISS move the data.

Experience from previous migrations show that it is very easy to make mistakes, fail to transfer data you cannot read, people are on parental leave, etc.

The PI (or another person the PI delegates this task to) can request a data transfer from NAISS using the command storagemigrate on Tetralith (recommended) or by contacting NSC Support. You will then be asked to provide the "what" and "when" for the data transfer.

We will do our best to transfer your data on the date you have chosen. If we need to change the schedule we will inform the person that made the request.

You can change or cancel your request by simply re-running storagemigrate later. Around 7 days before the requested date, we will start a preliminary transfer of data (to speed up the final one). This data is transferred in the background but will show up in the storagequota output on Arrhenius. Once the background transfer has started you will need to contact NSC Support to change your request.

storagemigrate will warn you if you request a date when other projects have already scheduled a large amount of data to be transferred. If you choose that date anyway your transfer is more likely to be delayed. Projects are transferred in the order they submitted their request.

You can use the command storagemigrate_overview to see which days other projects have already requested transfers. If possible, try to request your transfer for a day that is less busy, it will speed up your data transfer. storagemigrate_overview will also show ongoing transfers so you can use it to see if the transfer has started.

We will send an email notification to the person that submitted the transfer request when the transfer starts and when it is completed.

The options for what the project wants NAISS to transfer are:

• Request a full move - NAISS moves the entire project storage directory.

• Request a partial move - NAISS moves ONLY the data you have put into the "to-arrhenius" subdirectory (e.g /proj/someproject/to-arrhenius) This can be useful if your data does not fit into your storage allocation on Arrhenius and you want to move most of the data to Arrhenius now but leave some on Tetralith to be handled later. You need to create the to-arrhenius directory.

• No move - the project will move its own data

• No move - the project has no data that needs to move

(the last two options will be handled in the same way by NAISS, we just want to know the reason for why you did not want any data to be moved)

The options for when the project wants the transfer to happen are:

• Starting as soon as possible (if no other transfer is ongoing the transfer should start within 10 minutes)

• Starting on a fixed date, e.g "2026-07-14" means "starting 2026-07-14 as soon as possible after 00:00 CEST"

• Starting the day after Tetralith is shut down (as this is planned for 2026-09-30, the transfer will start as soon as possible after 2026-10-01 00:00 CEST.

As the system is automated transfers can start at any time including weekends, but staff will only be able to handle problems during normal working hours.

If a project has not requested a transfer or a "no move" by the time Tetralith is shut down, NAISS will move the entire project storage directory to Arrhenius. This is done so that projects who do not read this document (parental leave, etc.) will not lose data.

Each project can only request one data transfer.

NAISS will only move data, not copy it. If you absolutely need a writable copy left on Tetralith, contact NSC Support to discuss your options.

Data will be moved to the from-tetralith subdirectory of your Arrhenius project storage directory, e.g /proj/DIRECTORYNAME on Tetralith will be moved to /nobackup/proj/disk/DIRECTORYNAME/from-tetralith. This is done so we don't overwrite data you have already created on Arrhenius or data that is being migrated from Alvis. You can then move the data from from-tetralith to another location in the project storage directory tree, or leave it there.

Due to the large number of projects to be transferred we have a very limited ability to accommodate any custom requests outside of the options described above. If none of the above options work for you, contact NSC Support.

Since most projects will get a smaller storage allocation on Arrhenius, most projects will need to remove or move some data before the data can be transferred.

It is the project's responsibility to make sure that the data you request a transfer for will fit into your storage allocation on Arrhenius!

If the data you requested a transfer for will not fit into your storage allocation on Arrhenius the transfer may fail or you may end up being over quota on Arrhenius.

When the data transfer begins, the data becomes inaccessible on Tetralith. When the data transfer is complete, the data will become accessible on Arrhenius. I.e you will never see partial data anywhere and you will not be able to access the data while the transfer is in progress.

The transfer will take some time, from minutes for small projects to maybe a day or more for the largest ones.

The transfer will normally start at 00:00 CEST on the day requested, but if many projects choose the same day, we will not start all at the same time. In this case, transfers are started in the order the transfer request was made. So if you still see your data on Tetralith at 01:00, that is not necessarily an error.

If you request a partial transfer of data and leave some data behind on Tetralith after the shutdown date, you will then have 14 days to retrieve this data (i.e until 2026-10-14). NAISS will then inform the PI's university, give them 14 days to retrieve the data and then delete any remaining data. This is an accelerated version of the normal NAISS Data Decommissioning process

Moving data from user's home directories to Arrhenius¶

When migrating from Alvis¶

See the Alvis data migration page

When migrating from Tetralith¶

Data in a user's home directory (/home/USERNAME) will not be automatically transferred to Arrhenius.

The main reason for this is that many users are members of several projects that will probably not move to Arrhenius at the same time, so NAISS cannot know when we should move a specific home directory.

Instead, a command copy_home_directory_to_arrhenius is available that you can run on Tetralith that will copy the contents of your home directory to Arrhenius. To ensure that you can still use Tetralith afterwards, the home directory is copied, not moved.

The data will be copied to a subdirectory "from-tetralith" in the Arrhenius home directory in order not to overwrite any Arrhenius settings or data that might already be there.

The script will ask for confirmation before doing anything and show you the rsync command that will be used.

If you leave any data in your home directory on Tetralith, you will have 14 days after the Tetralith shutdown date to move that elsewhere, then anything that remains will be deleted.