Shared Data Storage
All FLC hosts have access to the /data directory of flcl01, the FLC group server. It is automounted via NFS under /nfs/flc/flcl01. Due to the mechanism of automounting, that directory will appear empty until you explicitly change into the subdirectory data. In the same way, the mass storage of the cluster servers lc3 and lc4 appears under /nfs/flc/lc3/pool and /nfs/flc/lc4/pool respectively. Go and talk to one of your administrators if you need a personal directory on one of the servers. In the opposite direction, the /data directories of all FLC desktops are available on flcl01 under /nfs/flc/hostname/data. Please note that accessing the NFS through the shortcut path /flc is deprecated.
Like most DESY groups, the FLC group has a common AFS directory under /afs/desy.de/group/flc. On the FLC hosts there should also be a symbolic link /group which points to the same location. Under /group/pool/username, every FLC user should have 200 GB of storage space at their personal disposal – talk to your administrators if you don’t own such a directory yet. As usual in the AFS, the .OldFiles directory contains a read-only snapshot of your files that gets updated every night, but apart from that, there is no further backup.
You can find some preinstalled software and certain shared documents in other subdirectories of the /group area. The directory /group/bin will even be included in your predefined PATH, so you should be able to use group-specific software without effort.
The group servers flcl01, lc3, and lc4 have direct access to the DESY dCache, which is a huge central mass storage system. Its contents are mounted via PNFS under /pnfs (similar to /acs in other computing environments). Every FLC user should have their personal directory under /pnfs/desy.de/flc/users/username – tell one of your administrators if you haven’t been included yet. Note that PNFS is only a pseudo-filesystem: It will display the contents of the file catalogue (i. e. the directory structure, file names, file sizes, modification dates, access permissions, …), but it will not provide access to the stored data itself. This means that commands like mv, rm, ln, touch, chmod, etc. will work as usual, but cp, cat, and everything else which tries to read or write the actual contents of the files will fail. Instead you can:
use the dccp command to transfer data to and from the dCache
put the preload library libpdcap.so into your LD_PRELOAD environment variable to make ordinary programs dCache-savvy
write your own programs which make use use of the library libdcap.so
See the dCache FAQ for some further details.