Policy by Folder

Rationale for Proposed Policy

Please see the children pages Version 1, Version 2 and Version 3 for a description of the evolution and rationale of the LCLS data retention policy.

Notes

• Please do not store under the scratch folder data that you cannot recreate because this directory is not backed up and the oldest files on scratch may be deleted at any time to make space for data from new experiments.
• The tape archive (xtc, hdf5, usrdaq) and the tape backup (results, home) are fundamentally different:
  • In the tape archive the folders are frozen after the end of the experiments and their contents are stored on tape once. 
  • In the tape backup, the system takes snapshots of the folders as appear at a given time. this implies that files which are deleted from disk are eventually, i.e. after a long enough time, also deleted from tape. 
• For raw data the cleanup operations will affect all files, i.e. all streams and chunks, which make up one run, rather than individual files.
• After 2 years from the end of an experiment we'll remove the experiment from disk. At that point we'll take a snapshot of the results and calib folders and archive them to tape so that we can, upon request, restore an entire experiment back to disk.
• After 10 years we plan to remove the tapes with the archived raw data from the silos and store them in a safe environment.
• The new policy will apply to all experiments, i.e. it will be retroactive, and its deployment date will coincide with the start of Run 14 (August 10^th 2016).
• For questions regrading the data retention and data access send your question to: pcds-datamgt-l@slac.stanford.edu.

User Home

• Please do not store large files under your home, this space is meant for code/scripts, documents, etc, not science data.
• Users can check the used and available space under their home with a command like:

df -h ~<username>

• Users can automatically access snapshots of the backup of their home here:

~<username>/.zfs/snapshot/