How is my account backed up?

• Nightly incrementals are run each night. Files modified in the last day are copied to a large, specially indexed, filesystem and are kept for approximately 4 weeks. After this time the most recent updates are collected together to make a weekly incremental, compressed, and stored for another 6 months (and possibly longer depending on available space).
  
  These backups are normally used for restoring individual files which may have been lost or damaged. The incremental backups cannot normally restore a complete directory.
  
  
   These incrementals are effectively online and can be restored easily using the `tkrestore' command. See also, the Restoring deleted files FAQ page. Only files changed and backed up in the last 6 months will be listed by tkrestore.
  
  
  Because of the space limitations on the backup filesystem, a filter called `buff' is used to select the files to be backed up. A full description is in the manual page, however the main effects of buff are to:
  
  
  • omit files which seem to be easily reproduceable (eg, .o, .dvi),
  • omit singularly large files,
  • limit any filetree to some designated size.
  
  
  All of these limits can be changed (see the manual page for buff) EXCEPT for a limit of 50Mb per person per night (because of the limited space on the backup filesystem). That is, only the first 50Mb worth of modified files per person are backed up each night.
  
  
• Full dumps are a complete dump of the contents of each home directory. As long as the home directory can fit on the backup media, the home directory will be backed up on Full Dumps. Note that the current media used for full dumps (LTO tapes) can hold up to 180Gig (compressed).
  
  There are three classes of Full Dumps taken throughout the year:
  1. Regular full dumps of all home directories, taken every 28 days, and kept for two years;
  2. Session full dumps of all home directories, taken a few weeks after sessions one and two every year, and kept indefinitely;
  3. Archive full dumps of expired home directories, taken a month or so after they have expired, and kept indefinitely.
  
  
  Full backups are normally used when:
  • There are no copies of the missing file on incremental dumps. This will happen when the file to be restored:
    • Had not been modified within the last 6 months or so;
    • Had not been backed up onto incrementals because of buff limitations.
  • A significant part of a home directory has been lost.
  
  
  
   Files can be restored from full dumps by SS. See also, the Restoring deleted files FAQ page.
  
  
  
• Snapshots are taken once every 8 days of the file systems on most of CSE's major servers - particularly of the major file servers hosting user directories. Snapshots contain a complete dump of the entire filesystem, and are stored on 4 duplicated sets of 8 LTO tapes rotated over 32 days, with one set of 8 being stored off-site.
  
  These backups are normally used when there has been a major disk catastrophe on a server.
  
  
   Files backed up to snapshot can be restored by SS.