Contents of system and user directories (with the exception of the /tmp directories) are backed up to Digital Linear Tape on a daily basis. This applies to MACH, HYDRA, NESTOR and the Sun servers.
There is no fully automated system to reload files removed by the user. To request a reload of a file, invoke the command
on MACH or HYDRA and answer the questions. A request will then be sent to the Computer Room operator. You will be informed by an electronic mail message when the reload has been completed or if it turns out to be impossible to reload your file(s).
See the example of questions asked.