Differential Backup Method
There is a significant, but sometimes confusing, distinction between
differential backup and incremental backup. Whereas incremental backs
up all the files modified since the last full backup or incremental
backup, differential backup offers a middle ground by backing up all
the files that have changed (file is changed if content, attribute or
access permition rights are changed) since the last full backup.
That is where it gets its name: it backs up everything that's different
since the last full backup.
Restoring a differential backup is a faster process than restoring
an incremental backup because all you need is the last full and
last differential backup.
Use differential backup if you have a reasonable amount of time to
perform backups.The upside is that only two backup container files
are needed to perform a complete restore. The downside is if you
run multiple differential backups after your full backup, you're
probably including some files in each differential backup that were
already included in earlier differential backups, but haven't been
Differential backup is gaining in popularity because
it traps files at points in time, for example, prior to virus
Advantages: restore is faster than restoring from incremental backup, backing up is faster
than a full backup, the storage space requirements are lower than for full backup.
Disadvantages: restore is slower than restoring from full backup, backing up is slower
than incremental backup, the storage space requirements are higher than for incremental
See also: Mirror Backup Method