Helping people with computers... one answer at a time.

There are several ways to approach storage space for backups (compression, increments, differentials). Some will be tricky, and in the long run, a new hard drive just might be easiest.

Hi. On my computer at home, I have 800 GB of data. My external storage is 1000 GB and I use Acronis from your recommendation. I have a backup of my computer and then weekly, I do differential backups, but the storage is becoming full. So I had to delete the external storage and start again. So for five hours, if my computer broke, I was going to lose everything. Is the only solution to buy a bigger external storage?

In this excerpt from Answercast #11, I look at the issue of storing backup files, explain different methods of storing backups, and look at what might be the easiest solution to a large data problem.

A bigger hard drive?

It's not the only solution, but it is certainly a solution and it might even be the easiest solution.

There are a couple of different approaches you can take.

One is to crank up compression.

Acronis and similar backup tools usually have the option to compress the data that they're backing up. The default is typically what I would call moderate compression. They can usually be turned up so that they'll compress the data a little bit more. The actual backup copy then would take up less space.

The cost is that the backup might take a little bit longer because you're actually asking the CPU to do more work as the backup happens.

Another option is: instead of using differential backups, use incremental backups.

The difference is actually simple. You started out with a full backup (which I assume is the five hours initial backup that you started with), every backup thereafter can be either incremental or differential.

  • Incremental says, "Save the changes since the previous backup." Those are typically fairly small or small in comparison.
  • Differential backups are backups that include everything that changed since the full backup was taken.

A differential backup would get bigger every time you take it until you run out of space. An incremental backup would actually vary in size because its size will depend only on what has changed since the previous incremental backup. So, that's another option.

Certainly getting another hard disk is a very simple option.

Creative system images

The other approach (I'm a little reluctant to go this way) is to consider whether or not everything on your primary hard drive needs to be backed up or needs to be backed up all the time. One solution is to take a system image - an initial system image - and save that in a different place, or on a different platform, and then selectively choose what to backup on a more frequent basis.

I suggest that only because it's certainly a possibility. I'm reluctant to suggest it only because you do run the risk of not necessarily backing everything that you wanted to.

Less frequent backups

Another approach, of course, is to do less frequent backups. In fact, I ran into this myself several years ago, I had Acronis doing a full backup followed by nightly incremental backups.

My hard drive (my backup drive) got full. So, I made a choice to do incremental backups every other night instead. The same could apply with a solution that still uses your differential backups.

So, there are a lot of different approaches to solving this particular problem. You can reconfigure your backup to do things a little bit differently.

Cost of a hard drive

By far, the simplest, (even though you already have a pretty big drive at a terabyte) is to go out and get another hard drive. Get one that is as large, and come up with a way to spread the backup across the two drives (which is not necessarily an easy thing to do). Or go out and get yourself a new even larger one.

I believe they just released a three terabyte for not that much. I know that I have series of two terabyte drives in my basement right now.

So there are definitely some easier options there with respect to simply getting larger hard disk. In all honesty, given the price of hard disks these days, that's probably the easiest and safest way to go.

Next - How do I stop automatic emails coming out of Hotmail?

Article C5236 - April 22, 2012 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

April 24, 2012 9:11 AM

I too used to save backups until I ran out of room, delete the oldest, and continue. But I realized that while I might need to access any of the most recent backups, I probably wouldn't need every single older backup although occasionally I might want to recover something quite old. So now have a scheme where I keep a sparse set of very old backups, a more dense set of intermediate age backups, and all recent backups. For me that seems to make the most effective use of the amount of storage I have available.

Les Ashton
April 24, 2012 4:23 PM

Hello everyone (and thank-you, Leo), I am backing-up weekly on a Maxtor OT3 80Gb external (not using compression at first; very old unit, gone out of production, now administered by Seagate) coupled to my Asus main machine, after having backed-up to DVDs for some time. At that time Seagate was not too satisfactory as a source of advice for young players, so got myself a 3/4-T WD disc and looked for a backup program to use with it. After mucking around with a couple which made accessing data difficult, decided the WD was too slow anyway, so turned that into storage for videos and applied compression all-round (main + Maxtor) with a Toshiba 18Gb thumb-drive for run-of-the-mill and as a refuge to save to when my archaic E (data) internal drive drops out. Seagate seems to have practised a bit of digital-extraction since my earlier disappointment, and now appears to provide more support; but I shall have a good hard look at your recommendation of Acronis. Once again, thank you -- I welcome any helpful comments from my hideyhole in SandGroperLand. Cheers, Les A.

charles simkins
April 24, 2012 8:53 PM

First off, 800 GB of stuff stored on a hard disk is really over the top. Now I would recommend categorizing the stuff you are storing. If it is movies or TV programs that will eat up a lot of space and the best bet is to stick those things on a separate hard drive as they don't change and the drive is not used that often so the risk of losing stuff relates to how much it is valued. Then look at keeping the deleted files storage cleared out. But 800 GB seems like a lot of stuff that is not that valuable to keep backed up. Music can take up a bit of space as well and can be relegated to an external drive as well.

April 25, 2012 3:48 PM

Acronis Home 2012 also has a backup theme for single full copy back up.

That one made the most sense for me. The main back up file size remains fairly constant because things aren't piling on top of it so the drive doesn't prematurely fill. (I have also read complaints about corrupt incremental/differential files not intergrating back in on a restore.) I back up once a week.

The thing is with the auto mode or manual Single Copy backup, by default, Acronis Home 2012 actually makes a second full backup before deleting the first. The concept is this: if something crashes and the hard drive fails before a complete backup finishes, there's still a good backup available.

There has to be room for the second backup which means you need at least twice the storage capacity as your backup needs normally require. That may present a problem.

With my 160 GB primary drive which backs up to a 500 GB external drive, it's fine. Run and done.

My other drive is a 70% full 1.5 TB hard drive that I backup to a 2 TB external drive. I have to manually delete the existing back up file for the new one to fit. I have to do that first or the backup stops with an "out of space" message and then I have to delete the existing backup within 10 minutes or the backup fails. So much for real protection if something goes bad! If it wasn't for the email operation summary the program provides I wouldn't notice the backup had failed. There don't seem to be any other indicators.

I could add another drive but don't want to spread a single backup across multiple drives. I'll eventually get a 3 TB external drive but they still cost in the $200 ballpark.

Just remember, pay attention to storage requirements your software and backup1 plan will use.

I'm hoping someday we see the higher capacity Blu Ray DVDs in an r/w for backup hard copies a home user could create...

Comments on this entry are closed.

If you have a question, start by using the search box up at the top of the page - there's a very good chance that your question has already been answered on Ask Leo!.

If you don't find your answer, head out to to ask your question.