Leo, Don’t you think you neglect incremental backups as being as important,
if not more important, than system backups? One of the questions that I
submitted in the past two weeks had to do with how you use a backup from one
system if the machine dies and you purchase another brand. Wouldn’t incremental
backups be more important than a system backup if system backups would be
useless with a brand new computer?
In this excerpt from
Answercast #8, I discuss the various types of backups, when and how you
should use each strategy, and give my recommendation.
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Incremental backups are important
I think there’s a little confusion. First of all, I certainly don’t neglect
incremental backups. I think that they are a critical part of anyone’s backup
A system backup and an incremental backup are two terms that actually don’t
- Full backups with incremental backups and
- System backups versus data backups.
So, I want to talk a little bit about what those terms really mean – at least
the way that I use them.
One of the problems with some of these terms of course is that there is not
necessarily a generally accepted definition. Sometimes, people will use them and
mean something slightly different.
A system image backup
That includes Windows; it includes the boot sector; it includes all of your
installed programs; it includes all of your data.
A data backup
A data backup backs up only the data files on your computer.
What to backup?
Now, the question is: what’s a data file? Well, that’s where things get
sticky because many programs that perform only data file backups make some
assumptions. For example, they might assume that you put all of your documents
in My Documents.
Well, that’s not where I put my documents. I put them all over the place and
I want all of that other stuff to be backed up. But fundamentally, the data
backup is just that; it backs up some definition of what it thinks of as your
data files – or some subset of the files that are on your computer.
It makes sense that those kind of backups exist because not only are they
faster and smaller, those are the kinds of backups that work well if you’re
doing something online (if you’re backing up to an online backup service).
Backing up your entire system (doing a system image) online is impractical.
Typically, the system image is huge, big, compared to the speed at which you can
Data backups, on the other hand (backups of just the data files), are useful
in a case like that because no matter what (you could lose your entire
computer), but you still have the files that you care about; the data files that
you care about.
You could reinstall Windows; you can reinstall your programs, but there’s no
way to recover your data unless you actually have your data backed up
System or data?
So, when I talk about system or image
backups, I mean your entire computer, entire hard disc.
When I talk about data backups, I’m talking about just the
data files on your system.
Full vs. incremental
Now, a full versus an incremental backup. The confusion is probably that an
incremental backup typically starts as a full system backup; a full backup of
your entire machine.
An incremental backup then says, “OK, I’m going to back up only what has
changed since the previous incremental backup and if there wasn’t an
incremental backup previous, then from the previous full backup.”
What that means is that:
- On day one you do a full backup.
- On day two, the backup includes only those things that changed during day
- On day three, the backup includes only those things that changed during day
- On day four, it includes only those things that changed during day
Now, I have not talked at all about the difference between data and system
files. For a properly set-up backup, there is no relationship in this particular
strategy. An incremental backup will back up whatever has changed: be that your
data files, be it the registry, be it a new program you installed –
That’s one of the reasons that incremental backups are so important. They
bring your system up to the time of when that backup, that incremental backup,
Incremental requires a previous full backup
The downside to an incremental backup is that in order to use it, you need
the full backup that it’s built on – plus all of the incremental backups in
between the time you took that full backup and the time that you want to
So, for example, in that scenario that I just outlined: where we have a full
backup on day one, an incremental on day two, [and] an incremental backup on day
three. If we (for some reason) want to restore our machine to the condition it
was in on day five, we need to have in our possession (for the backup program
to use) the full backup from day one, the incremental backup from day two, the
incremental backup from day three, four, and five. So it gets a little bit more
You could take full system backups every time if you wanted to, if you’ve
got enough space and enough time to take the backup.
The nice thing about incremental backups is that they’re typically smaller
and faster because they’re only backing up things that have changed.
So, I do think incremental backups are incredibly important to keep your
What I typically recommend is that you schedule your backup software to do a
full system image backup once a month and then do incremental backups on top of
that every night.
That worst-case scenario at the end of the month – if you need to restore
the computer to the incremental backup of last night – you will need the
initial full backup and all 30 or however many incremental backups. But that’s
the trade-off between incremental backups being so much faster and so much
Restoring to a new machine
Like I said, I think there’s some confusion in the terminology and the
In this scenario that you sort-of outlined where you’re trying to backup from
one system to another, it doesn’t really matter whether you’re using the full
backup or incremental backups. The problem is that this backup that you’re
starting from, that you’re required to lay down first, is for a different
To install a backup of any kind (including a system image backup) from one
machine to another, you start running into problems with things like device
drivers. The backup contains device drivers and settings for the computer that
it was backed up from, which is not necessarily the same as the computer it’s
being installed onto. Therefore, Windows may not work.
An incremental backup on top of that is absolutely critical because as you
point out, that’s where your data files are going to be. So I don’t see the two
as being mutually exclusive. I do think that they’re very complementary and I
think that it’s mostly about just a confusion in terminology.