Computer Backup Policies

Purpose of Backups

There are two reasons to run backups, to recover the contents of a disk in case of disk failure (commonly referred to as "backup"), and to checkpoint versions of files for later retrieval (commonly called an "archive"). The backup function requires only the latest version of each file on the system. Older backup versions can be deleted. The archive function requires several snapshots of the system be kept for some period of time. Older archives can only be deleted when it is determined that the data is no longer needed.

The CSG runs automated backups of most computers in the laboratory. We cannot run automated archives; we cannot determine which files need to be archived, nor determine how long to keep files. Users who want to archive their files to protect against accidental changes, for historical purposes, or to make space on their hard drives can do so, however the user needs to manage these archives.

Backup Goals

  • In case of disk failure, restore all files on a server disk to the previous day's version
  • Provide one year of old data backups stored on servers
  • Return a PC to a working state following a disk failure on a critical disk without reinstalling all applications or manually entering user preferences
  • Provide two months of old backups for PC's
  • User-initiated and archive backups are not deleted automatically; for now, they are kept indefinitely

We keep old backups so we can recover files that are accidentally lost or destroyed, however we do not have the resources to keep backups for indefinite periods. Since server backups are kept longer than PC backups, we strongly recommend that you keep important data on a file server. Also, we do not have the resources to backup the entire drive on every PC. Limitations are described in the section "What is backed up".

Note: For automated backups to work, your PC must be running and connected to the network during the backup time frame. If you shut down your PC at the end of the day, it will not be backed up.

All desktop PCs set up by the CSG are configured for automatic backups. Laptop computers are not configured for automatic backups, as they are usually not turned on during the backup window. Laptop users may perform their own backups manually. If you have a laptop that stays at LLE and can be left on, you may request that it be added to the automated backup schedule.

Exceptions to these policies may be made at the discretion of the CSG Group Leader.

What is backed up?

On PCs

There are two different partitioning schemes currently in use at the laboratory. Most new desktop deployments (i.e., machines outside the OMEGA and OMEGA EP laser systems) use the T Partition Scheme. Machines in the Laser Facility and many older machines use the C Partition Scheme. In either case, the backup policy is effectively the same. All local partitions except P:, Q:, R: and S: are backed up daily. If the system has a T: partition (the T Partition Scheme) then all user data should be stored on it (the Desktop, My Documents and Application Data folders are automatically stored on the T: drive if one exists).

There are limits to the amount of data that be backed up each night. For this reason, C: and T: partitions are typically limited in size. Extra local disk space is normally allocated to the P: partition. Users are welcome to use this space, but it is not backed up and will not be restored in the case of a disk failure or system upgrade.

On Servers

All partitions on servers are backed up daily, except for temporary system space, and those partitions specifically designated as temporary space (e.g., /local on computing servers, or /theory on ash).

Hopi, Sequoia, Redwood, Sassafras, and Mahogany are servers.

Special Note on OMEGA and OMEGA EP PCs

Machines on these networks are backed up as described above. In addition, PCs in these facilities may also have special disk imaging software installed to speed system recovery in the event of a disk failure. These disk images are independent of the normal backup procedures described here.

Schedule

Automated backups begin at midnight. On working days (Monday through Friday), if there are no problems, backups are finished by 6:30 AM. On Saturdays we run more comprehensive backups that may continue into the afternoon.

Not every file is backed up every day. We do this to limit the amount of data in the backup system.

The different types of backups are:

  • Full: Every file on the system is backed up. This occurs once a month, on a Saturday.
  • Cumulative: Every file that has changed since the last Full backup is backed up. This occurs on Saturdays when a Full backup is not run.
  • Incremental: Only files that have changed since the last backup (either Full, Cumulative, or Incremental) are backed up. This type of backup is performed Monday through Friday.

If you have questions or comments about the backup policies, please contact a member of the Computer Support Group.