ComputingResourcesUserGuide

Version 11.1 by erlandm on 2020/02/27 10:41

Brief Guide to Computing Resources at FLASH

Introduction

As explained in the User overview page the data recorded at FLASH is stored in an internal DAQ format (.raw) which is converted with a few minutes delay to easily accessible HDF5 (The FLASH HDF5 structure) files which are the basis for data analysis. These files are stored on the ASAP3 File System which is accessible from DESYs Maxwell Cluster which is recommended to be used for the analysis by users. A library provided by FLASH ( BeamtimeDaqAccess ) allows efficient access to the recorded data in the HDF5 files. In addition the HDF5 files are accessible from the beamline computers and via a web interface: Gamma Portal

Access to the Maxwell cluster

The Maxwell Cluster is a powerful farm of inter-connected PC nodes running Scientific GNU/Linux. To access the cluster you need a DESY AFS computing account or a so called scientific account (PSX).

PSX account

The scientific (internally called: PSX) account is a "real" account that is needed to be able to log into DESY computers ( mainly used for Maxwell). This is different from the DOOR account that you need for administrative purposes to be registered for the experiment, do safety training etc.

To get a PSX account please talk to your local contact well before the beamtime. The local contact will take care of the paper work and send you more instructions.

Scientific account (PSX) users instead go to desy-ps-cpu.desy.de. To connect to the Maxwell cluster from outside the DESY network -- eduroam or the DESY guest network are considered to be outside -- then you can SSH tunnel your connection through desy-ps-ext.desy.de or more conveniently directly use the remote login to max-display.desy.de.
If you have a default DESY AFS (DESY employees) account login to max-fsc.desy.de using your personal account. (From outside of DESY network tunnel through bastion.desy.de or use the remote login to max-display.desy.de.

Note: Please, always do use your personal account to work on the Maxwell cluster or any central DESY computing resources. Don't use the functional accounts like vuvfuser or bl1user. Using functional accounts on shared resources causes many difficult to predict problems, even if it might appear to work for you in the beginning. Also, never try to login to bastion, desy-ps-ext, or max-display using one of the functional accounts.

Maxwell cluster

The extensive documentation can be found at Maxwell Cluster

In particular we want to mention the option JupyterHub on Maxwell , available Software , for more advanced computing demands Running Jobs on Maxwell.

Where to store data

There are a number of data stores not linked to the ASAP3 file systems available to cover for storage needs unrelated to experiments or beamtimes. Our page "Where to store data" presents an overview of the storage resources and the unified access to disks on DESY's GNU/Linux and MS Windows PCs.