The basic difference between incremental and differential backups is that
both start by making a copy of the files to be backed up. Then the
incremental backup makes a copy of the files that have changed since the
last backup was done. Assuming daily backups, on day 1, all files are
copied. On day 2, the files that have changed since day 1's backup are
copied. On day 3, the files that have changed since day 2's backup are
copied, etc. This results in smaller backup file sizes but means that all
files must be restored starting with day 1's backup followed by restores of
each succeeding backup to get back to the file status as of the last backup.
The differential backup makes a copy of the files that have changed since
the original backup. So on day 1, all files are copied. On day 2, the files
that have changed since day 1's backup are copied. On day 3, the files that
have changed since day 1's backup are copied, etc. This results in larger
backup file sizes but means the the files can be restored starting with day
1's backup followed by a restore using the latest backup. So, in a nutshell,
for incremental backups, the first and all succeeding backups must be
restored; for a differential backup only the first and the last backups must
be restored. If speed of restore is not a concern but space is, use an
incremental backup method. If speed of restore is a concern but space is
not, use a differential backup. Some people recommend in the case of
incremental backups to periodically make a new full backup to repeat the
process over again to reduce the number of backup files to be restored. Many
people recommend using Acronis for backups as it is much more flexible than
Vista's backup.
Tyro