The speed of a Time Machine backup or restore depends on a number of factors, and does take significantly longer than just copying some large files:

1. •The speed of your Mac
   

2. •The speed of the backup destination
   

3. •Other things running on your Mac
   

4. •Other Macs or processes sharing the connection to the backup destination
   

5. •The average size of the files
   

6. •Most important, the type of connection to the backup destination
   

For a full backup, full restore, or transfer to a new Mac via Setup Assistant or Migration Assistant, assuming little else running and minimum conflicts, you can expect, very roughly, the following average speeds, under average conditions for a relatively small system:

Gigabit Ethernet may be much faster, perhaps as much as 80 GB/hour, if the backups are on a NAS or a shared drive on another Mac that supports gigabit Ethernet (but not a Time Capsule).

Don't be alarmed if the initial estimate is much slower than shown above;  they're notoriously inaccurate at first, and the estimate usually comes down quite a bit as the backup progresses.

The size may be an overestimate, too, as some things are omitted automatically, such as system work files, most caches and logs, trash, etc.  See the tan box in question #11 for details.

Note that the speed may vary considerably during the process, especially at first, as it depends partly on what's being transferred.  Since many things have to be done for each file (various directory entries, links, etc.), the speed per GB will be slower while copying small files. 

Thus a full backup will start very slowly (as will the first backup after a system upgrade), because your Applications and System folders contain a huge number of mostly very small files, and are the first things to be backed-up. 

The speed will increase considerably when transferring, say, a folder containing many large video files.

If you have a large system, and/or many large files, you may see faster overall speeds.

If you get significantly slower average speeds, see Troubleshooting item #D2.

10-15 GB/minute 80-90 GB/hour

50-55 GB/hour

40-50 GB/hour

20-35 GB/hour

11-14 GB/hour

5/29/13

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