Smirnoff said:
I intend to purchase an external USB HD for back up purposes.
However, in the meantime I am using Acronis Secure Zone (ASZ).
After reading the Help file, I decided to do a full back up followed by a
scheduled differential back up (each week).
My understanding is that with differential back ups, you only need the
full back up plus one differential back up to restore (unlike incremental
back up which requires ALL files for this purpose).
As I am using my (only) HD, I want to keep allocated space as small as
possible.
I thought that differential back ups would overwrite any previous files.
However, today (scheduled back up) the ASZ informed me that I needed to
allocate more space, this I did.
I now have showing in ASZ recovery one full back up plus two differential
back ups. Obviously the last did not overwrite the previous.
How do I delete prior back ups?
Smirnoff:
First of all - and this is important if not vital - I would strongly suggest
that you *not* use your source disk (the HDD you're backing up) for the
"destination" disk for your backups. This is a very iffy proposition to say
the least. Should that day-to-day working hard drive become dysfunctional
for any reason you're in "nowhere land". I would strongly advise you to use
another HDD as your destination disk - either another internal HDD or better
yet, an external HDD (USB/Firewire/SATA). The fact that you're storing the
backup files (archives) in a "hidden partition" created by the Acronis
Secure Zone utility does *not* give you the kind of protection/security you
need for recovery purposes. I'm reasonably sure you've created - or shortly
will create - the Acronis "Bootable Rescue Media" CD, yes?
So please...consider using a HDD other than the source disk to store your
backup files. If you want to store them on a separate partition - hidden or
otherwise - on that drive, fine.
(BTW, all of my following comments apply to the ATI version 9 program. I
believe they hold true also for the version 10 program but my experience
with that latest version hasn't been as extensive as it has been with
version 9).
Anyway, as to your query...
Generally speaking we prefer to use incremental backups rather than the
differential backups in the Acronis program. We find - in general - there's
a speed advantage in creating the incremental backup files (archives) rather
than the differential ones. And that's an important consideration for us.
Then too - all in all in the final analysis- we don't find any appreciable
disk-space savings when using differential backups rather than incremental
backups. Anyway, we're not terribly concerned with disk space savings in
view of the high-capacity relatively inexpensive hard drives available
today.
It is true that *all* the incremental backup files (images) need be present
in order to effect a recovery of the (more-or-less) current system, i.e.,
the system as it existed at the time it was backed up by the last
incremental backup file. Note however that "generational" backups are
available when using the incremental files backup process. For example, if
incremental backups were made on 5/9, 5/12, 5/15, 5/20 - it would be
possible for the user to recover the system as it was when backed up by
*any* of those dates. Many users find this an important capability. Of
course you could achieve this generational backup capability as well through
the use of differential files, however, the size of the differential files
would ordinarily be larger although admittedly that is not a particularly
important consideration for us.
Now, I'll finally get to your specific query...
Using differential backup images (assuming one has no interest in
maintaining generational backup capability) you need to retain the
*original* backup image *and* - assuming you wish to restore the system to
its most current state as of the last differential image - the last
differential image you created. You can delete all the intervening
differential image files after creating the latest one.
Anyway...
Why don't you experiment with both processes - creating both incremental &
differential backup image files and determine if one process has more appeal
to you than the other. But promise me, whichever one you choose, you'll be
sure to store those backup files on a different hard drive than the one
you're backing up. OK?
Anna