Each user has a limited amount of backed-up storage in a home directory. The amount of storage is determined by the individual's status in the Department. See accounts for details on user quotas.

User home directories are backed up to magnetic tape on a daily basis. On the first Monday of every month, a full backup is performed. On successive Mondays throughout the month, an incremental backup is performed that contains the changes since the last monthly backup. On other weekdays, small incremental backups containing only the changes that were made since the last weekly backup are performed. These means that files can be recovered in the following states:

• Early morning on any business day in the current week.
• Early morning on any Monday of the current month.
• Early morning on the first Monday of the current or previous months.

Backups are performed so that the system can be restored in case of catastrophic failure, and shouldn't be depended upon for restoration of mistakenly deleted or damaged files. For such occurances, the Department file server takes hourly "snapshots" of all directories. From any directory physically (not symbolically) located under /home/f85, a hidden directory called ".snapshot" exists that contains snapshots of the system taken over the past two weeks. After changing to that directory, 'ls -al' will reveal the timestamps of the snapshots, providing sufficient information for users to locate a copy of the deleted or damaged file. Files within the snapshot directory can be copied to their original location directly using standard shell commands.

The Department provides several mass storage options for large pools of data that do not require backup services. Note well that any data stored in these locations are not backed up and will not be recovered if lost.

• /scratch is a local 20GB (or larger) partition on each Department machine. For systems on individual desks, this directory is owned and writable by the individual at that desk. When a desk is reassigned, /scratch will be erased and reassigned without notice unless previous arrangements were made. For lab machines, it is writable by all users. Since /scratch is local disk space, it is ideal for real-time computation output.
• /home/scratch is a 1.4TB NFS-mounted partition on all Department machines. There is no quota enforcement on /home/scratch. Users may create a single directory in the format /home/scratch/<user_id>. /home/scratch is not local storage; data should be not be stored there as they are generated. Instead, output to local storage first, then move data to NFS-mounted partitions for storage. /home/scratych is not backed up to tape, but it is a file system on a relaible RAID-5 disk.
• /tmp is a local directory on each Department machine, and varies in size. It is fast local disk intended for temporary storage. Files in /tmp not accessed for ten consecutive days are routinely deleted automatically.

Personal storage devices, such as USB pen drives, can also be used on departmental systems. They will be mounted under /media/<volume_name>/ when connected to a USB port and automatically unmounted when removed from the port (<volume_name> is the label assigned when formatting the drive). Only disks formatted with MS-DOS FAT filesystems (VFAT) are supported. Because FAT only supports filenames in 8.3 format (8 character name, 3 character extension), files with long names should be archived (with tar or zip) before storage on personal media.