Time Machine help - back up from an external?

[roland.g]

I was told today by an Apple retail employee that Time Machine will not back up from anything other than an internal drive and I wanted to confirm whether this was the case.

For example I have an iMac with a 750GB internal and I also have a 750GB external drive. I want to keep my iTunes Music and iPhoto libraries on the internal but keep all my movies on the external drive for space reasons.

I want to then use a 2TB external drive to work with Time Machine. I was told that if I want to back up the 750 "Movies" drive that I will need to manually copy it because Time Machine will only back up the path of those files and that drive can't be included in the backup.

To me this seems to go against what TM is about, since I then have to manually manage that part of the backup, adding new items, rather than getting the benefits of TM's incremental backup. Can anyone confirm or deny this.

Second question is regarding TM for multiple machines. Can a 2TB drive be used as the TM drive for both an iMac and a MacBook or will the drive need to be partitioned?

 

[ergdegdeg]

TM can backup the content of external drives. You just have to delete them from the list of folders and drives not to be backed up.

And the same HD can be used for several computers' backups.

 

[old-wiz]

I have time machine set up to exclude stuff on the external HDs, but only because it's just old backups. Never heard that time machine couldn't backup an external HD.

If you have 2 machines going to the same HD, it would be wise to partition the HD to prevent them from using up too much space and getting in each other's way.

 

[roland.g]

Thanks. The 750 I have is actually a pair of them, so one thought was to set it from JBOD to a mirrored RAID (would that be wise?) so that media drive is then redundant. Then my TM drive could back up the content of the 750 internal and the 250 internal in my MacBook. Not sure on partitioning, would a 750 and a 250 really get in each other's way. If I don't use the 2 750s in my JBOD case in a mirror and backup the one plus the internal to my TM drive, then the other 750 in that case could be used for my MacBook.

My iMac has been in storage for a year and is now getting used again and will be the main machine. Not sure how much will be on the MacBook and how much need I will have for TMing it.