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size, which is typically 2 TB. If the cost difference is small, as
it probably will be, you'll be glad for that extra capacity later on.
You can use a single drive to back up more than one Mac (as I discuss
later, in Choose Local or Network Backups and Backing Up a Small
Network , as well as more specifically, in the context of Time Machine,
in Use a Single Backup Disk with Multiple Macs ). And if you have two
or three Macs (give or take), each with only a modest amount of data to
back up, combining backups on a single drive makes sense. Be sure to
calculate the space needed (for both duplicates and versioned backups)
for all the Macs you intend to back up and add them together before
deciding which drive to buy.
Note: If you intend to store bootable duplicates for more than one
Mac on the same drive, each duplicate will need its own partition. I
explain how to set this up in Prepare Your Hard Drive .
At the moment, the best values (cost per gigabyte) are to be had on
drives in the range of 2 to 3 TB (terabytes). You should easily be able
to find a 2 TB external drive for under $150, and a 3 TB drive for under
$200. But prices vary according to several factors, including which
interface(s) the drive has; read Choose an Interface (or Several) , just
ahead, for details.
But what if no drive is large enough, even for backing up a single Mac?
Suppose you have an iMac with a 2 TB disk, of which 1.6 TB is used.
You'd want, ideally, 2 TB of space for a duplicate and at least 2.4 TB
for versioned backups. As I write this in mid-2013, the highest-capacity
individual drive mechanisms commercially available hold just 4 TB
each, but that's not necessarily a problem; you can buy enclosures with
two or more mechanisms in one unit for a total capacity of 6 TB or
more. (I say more about such devices in RAIDs and RAID-like Tech .)
Alternatively, you can get separate drives for duplicates and versioned
In any case, you're going to be laying out some significant money for
your backup drives, and I just want to say that I feel your pain. But
remember: the pain of losing your valuable data would be greater!
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