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I'm quite new to the whole Mac OS X and all of its services. I have my MacBook Pro now for about 3 months. What I wanted to do now is to setup automatic backups using the Time Machine. The situation is that I have an external HD with 320 GB of space. I'd like to partition that, since I'd like to reserve some partition for being used from Windows OS (for my other family members) and the other partition for doing the backups using Time Machine.

My question now is how much space you would (at least) reserve for your Time Machine backups? The system I'd like to back-up is my MacBook Pro notebook with a HD of 320 GB. Of course I cannot backup the whole (full) system (unless I use the 100% space of my ext. HD.

I just wanted to hear the opinion of some of you, who are already using Time Machine.


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up vote 2 down vote accepted

Of course it'll be best if you can get a big hard disk to use Time Machine effectively - however from your question, I am assuming that you have your reasons to not be able to get it.

In this case, I would recommend you to NOT use Time Machine, and manually backup. There are a couple of reasons for this :

  1. You can selectively choose to backup only the most important data
  2. The hard disk can be a single partition, and space can be effectively used.

If you have to use Time Machine no matter what, then I recommend you do this (if I read your question correctly):

  1. Set aside 30GB for that Windows-use partition - That way you can use FAT32, and both Windows and Mac can write to it. It need not be large because I am assuming you are using it to transfer data from your Windows machine to Mac.
  2. Dedicate the rest for Time Machine.

And please, have another TM backup disk once you are able to do so.

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Thanks for the FAT32 hint, I planned to do that already. But I don't use it for transferring data between OS's, I do that over the network directly. I'll get a bigger HD but for the mean time I wanted to use Time machine, also for trying it a bit out. So what I understand from your question, I cannot configure Time machine s.t. I can exclude certain folders to no be backed up??? – Juri Sep 1 '09 at 13:25
I refer you to this thread - Google keywords are "selective backup time machine". – caliban Sep 1 '09 at 13:29
Post in here for convenience and archival sake : Yes, in the Exclude Folder window click the + sign to add and choose your home directory then CMD+A to select all files and folders. Then hold CMD down and click on the single folder you want to include in the backup. Voila, now by excluding every other folder and file you are only backing up one folder. – caliban Sep 1 '09 at 13:29
Thanks for the friendly answer :) That was what I wanted to know and of course, I could just have Googled. – Juri Sep 1 '09 at 13:35
Oh please don't mistake me - not chastising you for not googling. Just provided the keywords for your reference that's all. :) Welcome to the Mac community by the way! – caliban Sep 1 '09 at 14:26

You should reserve at least the amount of space of your laptop HDD for your backups. Time Machine is smart enough to only backup the files that have changed. But if your laptop is almost full, you won't be able to go "back in time" so much because Time Machine deletes the oldest backups as it goes.

Disk space is quite cheap. A terabyte hard drive is now less than 100$. Apple also sells their own devices for backups: Time Capsule (300$). It also doubles as a wireless router and print server.

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what about if I reserve 200GB? Shouldn't that be enough and moreover, can I configure - or let me better say - exclude some folders for being backed-up?? I.e. the folder containing my virtual machines?? – Juri Sep 1 '09 at 13:14
If you allocate less space than the size of the drive, you're not getting a full backup. You can exclude files from the backup. – EmmEff Sep 1 '09 at 13:22

For any backup solution the bigger the better. You can purchase 1 TB external drives with Firewire & USB for $125 - 150... And while that can be considered expensive, consider what the purchase price was 1 or two years ago.

As a guideline:

  • Firewire 800 if possible, the speed difference is amazing!
  • Snow Leopard is almost a must. Once again there is a large speed difference between Snow Leopard and Leopard
  • Consider your exclusions carefully. For example, my default exclusions are here - Time Machine Information
  • A 320 Gb drive is asking for issues, since it's the same size. If your going to do that Time Machine won't be able to backup in depth.

Backing up in depth is quite important, simply because you have to ask yourself when did this file get deleted, or damaged? A week ago? Two days? Two hours? Two months? If your backup doesn't extend more than a day or two, you might as well not be backing up. A week? Or two weeks? Certainly, but what if the file was damaged a month ago?

A reasonable backup should give you at least 90 days of backup, why? For the backup in depth, but because with most backup systems, it gets too expensive to build the storage pool further... Tapes are typically around $30-75 (or higher) for around 60 Gb (compressed).

With TimeMachine, it's expensive, but typically not that expensive to go further...My Timemachine backup at work goes back to May... It's almost 3/4ths full... But it's available as I need it, and I'm storing other data on the drive as well...

For example, feel free to place content you don't want backed up on your time machine drive...

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Thanks for the info. As I mentioned above, I then partitioned my ext. HD and reserved 200 GB for Time Machine. This may not sound much, but for now I have a total amount of 60GB that has been backed up by Time machine. So it should be enough for now. Once it isn't I'll get a bigger HD of course. Regarding my exclusions. I just excluded my virtual machine folder since I wouldn't like to back up the whole HD of my Win installation :) And of course. Upgrade to snow leopard is a must ;) Thx for the info though. – Juri Sep 2 '09 at 15:22

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