|
Regular backups are made of the public UNIX systems of Academic Computing,
which include the AFS file servers and all of the central systems.
These backups are designed to protect against hardware failures and
short-term emergencies only. They are not permanent archives.
If you need to restore lost files, you should seek help promptly while the
backups are still available. Backup tapes are overwritten once they expire. The
backup scheme used for the AFS file servers and local disks are slightly
different. Most user files are stored in AFS.
Public workstations and individual compute nodes in the Beowulf
clusters are not backed up, since the system images are all identical,
and all user files live on the central file servers. On these computers, the
only local user files are in explicit scratch and
tmp directories.
All Files (Local Disk and AFS Files)
All files, whether local to a single computer or in the AFS system (visible
to all of the computers), are backed up using the following general scheme:
- A full monthly backup of the data, saved for 12 months.
- A full weekly backup, saved for one month.
- A daily incremental backup, kept for two weeks.
Files can be restored to the state they were in at any daily backup for the
past 14 days, the previous weekly backup, and to any monthly backup from the
past year. Files of users who have left and been removed from the system can be
recovered for up to one year.
AFS Files
User HOME directories in AFS, and any other special shared
data volumes in AFS, have an additional daily snapshot facility.
- A complete "snapshot" of the directory as it exists at midnight.
These daily snapshots are kept online until overwritten by the
next one. If you accidentally delete a file, the most recent backup can be
retrieved trivially, as long as you realize and seek assistance before
it gets overwritten at midnight. Retrieving files from yesterday's
snapshot can be performed without administrator assistance.
Timing
The exact time of the backups may be important to know when determining
which files to restore. This may change; consult with the system administrators
for the latest information. As of August 2003:
- All AFS backups are made from snapshots taken each midnight.
- The monthly backups are taken on the first of the month.
- Local daily backups start at 19:00.
- Local weekly and monthly full backups are made on Saturdays starting at
18:00. The first Saturday of the month is saved as the "monthly"
backup.
|
