StrongLink-to-Versity

16 Jun 2026

Overview

This page is meant for users who wish to quickly update their archival/retrieval scripts so that they work with the new HSM software by Versity. In some cases, it might be valueable to not simply replace the old slk commands by new commands but to rethink the process itself. The HSM system by Versity might offer a much more efficient ways to do what you want. If you wish to do this, please start with the Getting Started.

Versity organizes tape requests very efficiently. Therefore, there is no need to group retrieval requests by tape as was required for StrongLink.

Versity packs small files automatically prior to writing them to tape. Therefore, there is no need to pack small files on your side. Exception: You plan to archive 10 000 files of 10 kB size or similar. Please still pack your data in these cases. If you are unsure what to do, please contact support@dkrz.de .

Replacing slk commands

If you need to replace slk commands other than archive and retrieve, please have a look into the Getting Started.

Login

slk:

# using your default DKRZ user credentials
slk login

acli:

# using your default DKRZ user credentials
acli login

mount point:

no login required

Archive one file

case:

• source: /work/ab1234/c567890/file.txt

• destination: /arch/ab1234/c567890/

slk:

# transfer file
slk archive /work/ab1234/c567890/file.txt /arch/ab1234/c567890/

acli:

# create destination folder
acli mkdir -p /arch/ab1234/c567890
# transfer file
acli cp /work/ab1234/c567890/file.txt /arch/ab1234/c567890/

# ALTERNATIVE transfer file => set destination filename
# e.g. renaming possible
acli cp /work/ab1234/c567890/file.txt /arch/ab1234/c567890/renamed_file.txt

Note: If /arch/ab1234 exists but /arch/ab1234/c567890 not, the first command will create a file c567890 in /arch/ab1234 with the content of file.txt.

mount point:

not possible

Archive folder recursively

case:

• source: /work/ab1234/c567890/output

• destination: /arch/ab1234/c567890/output

slk:

# transfer files
slk archive -R /work/ab1234/c567890/output/ /arch/ab1234/c567890/output/

acli:

# create destination folder
acli mkdir -p /arch/ab1234/c567890/output
# transfer files
acli cp -R /work/ab1234/c567890/output/ /arch/ab1234/c567890/output/

mount point:

not possible

Retrieve file

case:

• source: /arch/ab1234/c567890/file.txt

• destination: /work/ab1234/c567890/

slk:

# transfer file
slk retrieve /arch/ab1234/c567890/file.txt /work/ab1234/c567890/

acli:

# create destination folder
mkdir -p /work/ab1234/c567890/
# transfer file
acli cp /arch/ab1234/c567890/file.txt /work/ab1234/c567890/

Note: If /work/ab1234 exists but /work/ab1234/c567890 not, the first command will create a file c567890 in /work/ab1234 with the content of file.txt.

mount point:

# run staging command beforehand to be sure that file is actually in the cache
acli stage /arch/ab1234/c567890/file.txt
rsync -av /arch/ab1234/c567890/file.txt /work/ab1234/c567890/
# will exit with an error if file.txt is not cached

Note 1: The mount point is meant for easy access to individual files – e.g. to check the header of a netCDF file or to peek into a dataset. It is not meant for the transfer of large amounts of data. Please use cp of ATLAS for this.

Note 2: We recommand to always run acli stage prior to accessing files via the mount point. If a cache cleanup process starts before the file was accessed, it might be removed from the cache causing the transfer to fail. Running acli stage is similar to a touch command with respect to the time stamp relevant for the cache cleanup.

Retrieve folder recursively

case:

• source: /arch/ab1234/c567890/output

• destination: /work/ab1234/c567890/output

slk:

# run slk_helpers watcher setup for recall + retrieval:
... watchers ...

# OR retrieve all files at once (not recommanded, when files are not cached)
slk retrieve -R /arch/ab1234/c567890/output/ /work/ab1234/c567890/output/

acli:

# create destination folder
mkdir -p /work/ab1234/c567890/output
# transfer files
acli cp -R /arch/ab1234/c567890/output/ /work/ab1234/c567890/output/

mount point:

Please use ATLAS for this purpose

Replacing pyslk

Work in progress

Replacing fsspec + slkspec

Work in progress

Details on acli

Location of token

• slk: ~/.slk/config.json

• Versity: ~/.config/acli/session.json

Commands

** StrongLink**	Versity	Meaning
slk login	acli login	generate a login token
slk archive	acli cp / acli upload	file transfer to HSM [1,2]
slk retrieve	acli cp / acli download	file transfer from HSM [1,3]
slk recall	acli stage	transfer file from tape to cache
slk move	acli mv	move files within HSM
slk rename	acli mv	rename files in HSM
slk delete	acli rm	delete file
slk mkdir [-R]	acli mkdir [-p]	create directory
slk chmod	acli chmod	change permissions
slk search	acli search	run search for files

[1] acli cp transfers data in the background between tape archive and Lustre filesystem

[2] acli upload transfer data from current system/node directly to the tape archive

[3] acli download transfer data from tape archive directly to the current system/node

Glossary

• online: a file is cached

• offline: a file is not cached

StrongLink	Versity	Meaning
recall	staging	transfer files from tape to cache
	release	allow removal of file from cache
		if it is already on tape