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General discussion

Time Machine Disc Sizing

Jan 26, 2008 12:06PM PST

How should one size the external disc used by Time Machine? In its recent release of Time Capsule, Apple offers external discs of 500GB and 1TB. 500GB is certainly enough for my application. Is there any way I can determine if I can use a smaller capacity drive?

Thanks.

Discussion is locked

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Time machine
Jan 26, 2008 11:12PM PST

The size of the HD used for Time Machine is important but is not a deal breaker.

The larger the drive, the more backup information you can store on it.
Time Machine works by backing up the entire contents of your hard drive. You do not pick and choose what files to backup, you get the whole lot.
That said, you have to have room on your Time Machine drive to accommodate all that data. Each time that TM backs up, it does it every hour, it performs an incremental backup, only copying those things that have changed.
A good rule of thumb would be to find out how much data you have on your hard drive, Select the drive/Get Info/Used, double it and get a drive of that capacity, at least. I would not go with anything lower than 200GB.

As TM moves along, and the drive becomes full, it will automatically delete the oldest files to make room for new ones.

As an aside, your new external drive should be initialized before you first use it. Although "most" drives will work as soon as you plug them in, this is because they are formatted as FAT or FAT32, you need a drive that is specifically for the Mac. Format the drive into 1 partition, HFS+(journaled) and as GUID for an Intel Mac or APPLE for a PPC Mac. (Disk Utility/Partition/Options) A drive that is formatted APPLE cannot boot an Intel Mac.

P

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Re: Time Machine
Jan 27, 2008 8:10AM PST

Thanks mrmacfixit for your response about sizing and disc formating. Re: sizing, my imac came with an about 150GB HD of which I have used 50GB (and not carefully since the drive is so big for my application - mostly web and email). From your mail, sounds 100GB is enough for Time Machine, and I should round that up to 200GB.

That confirms my suspicion that a 500GB time machine drive is unnecessary.

Did I get that all correct?

Thanks.

Cheers!

Dave

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Time Machine
Jan 27, 2008 8:52PM PST

Yes, 200GB should do you nicely.

You can always move up when the need arises.

P

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Re: Time Machine
Jan 28, 2008 3:27AM PST

Thanks.

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Depends...
Jan 29, 2008 10:44AM PST

My Mac has an 80GB Hard Drive. I have mapped around 100GB of my external hard disk to Time Machine. It really depends how big your drive is, what is being backed up, and how long you want backups to go for. I generally only need to use backup very, very rarely, and if so, i usually only need to go back to a very recent time, say, if i deleted a file by accident.

The likelihoods of most people needing 4 week old backups is rare, so chances are a huge drive isn't going to be overly beneficial.