RE: autosave/restore software fails

['Mark Rivers' <rivers@cars.uchicago.edu>]

Our experience is that save/restore generally works well.  We have 9
IOCs, and each has 2 save/restore files, one for motor positions, and
one for all other settings.  During this power failure 17 of the 18
restores worked fine, 1 did not.  That IOC was rebooted several times,
and it is possible that it was rebooted while the save file was being
written.  

I think some minor modicications to save_restore could make it much more
reliable:

- Multiple backup files, with a user-selectable number of backups and
schedule.  For example, copy the existing .sav file to a backup if the
current backup is more than X minutes old, and recyle file names after N
backups.  For example, with 60 minute period and 5 backups:
   auto_settings.sav   Now
   auto_settings.sav.1 300 minutes ago
   auto_settings.sav.2 240 minutes ago
   auto_settings.sav.3 180 minutes ago
   auto_settings.sav.4 120 minutes ago
   auto_settings.sav.5  60 minutes ago
The next time the file is written more than 60 miunutes from now, it
will re-use auto_settings.1.

- More common sense checking to see if the current .sav file appears to
be corrupted.