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There's a lot of talk generally about backing up, and a lot of confusion around System and Data backups.

I'd like these questions to be considered in the context of Mac only, so any advice on tool would be great.

I myself am confused about what strategies to take... a few questions:

  1. What are the pro and cons of backing up just data versus the whole system?

  2. Is it better to have different strategies for backing up the system versus the data?

Do any of the following concerns make sense?

  1. Is a system backup "different" or less accessible than a data backup, in that it's wrapped in some kind of weird image format, or is all backup just the same?

  2. I feel like backing up the system should be done less often than data?

  3. I feel like backing up the whole system using online solutions is overkill?

  4. If you have all the original "disks", is it necessary to do system backups?

  5. Should I just system backups, which of course includes all data, and call it a day.


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As an aside: Time Machine kind of does both. (Though it does not backup everything, it is sufficient in most cases.) – Arjan Sep 12 '10 at 18:10

This is based on Windows, the questions you asked are general about computers so I think what I write will apply to you. There is nothing special in this regard to a mac.

First part of your question

  1. Backing up data is generally what you want for just recovering documents, and the important settings. Backing up the whole system generally means taking an "image" or "snapshot" of the machine in its current state so that you can rapidly restore it to that point (data included) at a later date.

  2. If you don't mind a bit of work, generally I prefer just to back up data and use a system rebuild as an opportunity to re-evaluate my previous decisions on what to install - e.g. only reinstall what is required.

Personally, I usually perform a general install, get the system how I like it, take an image before installing critical utilities - Visual Studio, Office, VMWare Workstation etc. and then take another image after each of these utilities. I install them in order of how many updates the utility (usually) gets so I can rapidly go back to them.

For example, VMWare Workstation gets updated frequently, it is usually the last item I install so that if I need to do a restore, I can simply choose the one just before I installed that and get the system working very fast with VS and Office, then just install the latest current version of VMware Workstation. Then of course, I copy my personal data back.

This is overkill, but if you have the disk space free - why not!

Second part of your question

  1. Usually a full system backup is placed inside a compressed file of some sort, .Iso, .Bin, .Wim, .gho, just to name a few. (Not sure on a mac what a default is).

  2. Personally as I said, I just do a full system backup when I get a machine, then I pretty much do a data backup all the time - my computer continually synchronises with another machine - however I also do a manual backup once a week just in case of accidents such as deleting a file - as that would get synchronised over.

  3. Depends if you trust your house won't catch on fire! (or similar). Online backups are there for peace of mind - nothing else. Personally, if you are worried enough to consider one of these, an alternate good solution would be to buy an external drive and backup to that, then leave it at a friends house. That being said, online backup solutions do have a place, you may want to look at Dropbox ( or would say Mesh, but not sure you can still use that)

  4. Again, depends - do you want to spend an hour (or however long) installing the operating system followed by ages installing all your utilities and configuring your settings, or do you want to bung in a disk, choose the backup file and have the system back to exactly how it was when you took the backup.

  5. Depends how much hard drive space you have free. As I said, I only do it when I first get a machine and make big changes, but it is a personal choice you have to make. Hopefully with what I have written above, you can make an informed choice!

If you have any questions or want help on any point, please write in comments and I will be happy to help.

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hey wil, great answer man, thanks so much – andy Sep 12 '10 at 2:59

Nice work Wil. I wanted to add some Mac OS X specific things though.

Part 1: Data versus the whole system?

I would simply look at the practical implications. Disk space is cheap. Time is costly and not replaceable.

A full system backup with the Time Machine feature in OS X will make recovery very simple in the case of a hard drive crash. One of my client's drives died last week. Installation of the new drive and recovery of all the software and user data took about 2 hours from a firewire 800 Time Machine backup drive. Compare that to the task of reinstalling all of the applications (this was a graphics machine), finding the serials and installer disks, and trying to make it exactly like the client left it before the crash with an incomplete backup. That's typically a 4-5 hour task, a big headache and it doesn't include the download time for all of the mammoth-sized updates.

If you can't use TimeMachine, you might look at Bombich's Carbon Copy Cloner. It has an an option for incremental backups, meaning only changed items are backed up, and can be scheduled. Of course you don't get the versioning like with Time Machine.

In the event of a hard drive crash, a Cloner backup could be used to restore the data, including the system, back to the new hard drive. One possible hitch is if you were to purchase a new machine. The system on the backup would probably not be appropriate for the new computer. You still might be able to use Apple's Migration Assistant to pull the applications and user data back. In either case, your user data will still be available.

OS X Server is a little different story, but I'm assuming you're talking about plain old OS X.

Part 2:

A full backup is the way to go. I would recommend that only critical data be sent to an online backup. Sure, you could probably recover with a full online backup but, depending on your internet connection and the amount of data you have, it could take days. Plus online space is not such a bargain in large quantities.

Bless you for keeping the System Install disks. So many people give me a blank look when I ask for them (You mean those were important? What do they look like? I don't think we got any when we bought the machine). I might be able to install a system for the client from my own media, but some applications, notably iPhoto and iMovie, are only included on the original system install DVDs. Then the client is off to purchase an iLife box if they ever want to see their photos again.

But in reference to your question, keeping system disks will mean you don't absolutely need to do a full backup. However, be sure and keep track of the installs and serials for any other applications you have installed as well.


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again, thanks theo, great answer – andy Sep 13 '10 at 0:26

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