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Cache manager policy

/cache Backup policy:
- Files will be backed up to tape if their size is between 3 MB to 300 GB, and the file is older than the backup threshold (12 days).
- For files between 1MB to 3MB, user can call srmPut to backup them to tape library if needed. But srmPut will fail if file size is less than 1MB.

/cache Deletion policy:

- Any files that larger than 10 TB will be deleted from /cache file system, and a email will send to <user>

- When a project usage excess its quota and the Lustre file system reaches its deletion threshold, the oldest file which belongs to the project and satisfied the criterion "pin count = 0 AND backed up" will be deleted.

- When disk space is needed, the oldest files that satisfied the criterion "pin count = 0 AND backed up" will be deleted
- Files not accessed in 2 years will be deleted (so please tar them into larger files when you are done with them).

- Start September 2019, We will tar a directory which satisfy these conditions and delete the directory.

  1. the directory contains N+ small files (to start with N=5000 and will reduce on the way).
  2. there are no large files (all large files have been migrated to tape and deleted from /cache).

- Since small files are not written to tape and deleted, there is a soft limit of 1 million small files limit for each user. We strongly recommend users to store only large permanent files under /cache. If a project generates a lots of small files, please put them under /work or /volatile disks.