Redundant Time Machine Backup to Multiple USB drives

[Jim_Lafleur]

Hi,
With OS X Lion (10.7.5), is it possible to backup (Time Machine) to multiple external hard drives (USB)? I'd like to rotate 2 drives every week. Odd weeks the drive A would be connected. Even weeks, drive B would be connected.
I think the short answer is probably no, if we'd like it more automatic. But is there a way to do it manually with a little more user interaction?

 

[Weaselboy]

That feature came out in Mountain Lion 10.8 so won't work for you with Lion.

 

[Jim_Lafleur]

Yes I know. But isn't there a way to do it manually? For example, Drive A as been my Time Machine drive for the past 7 days. if I connect disk B (which was used last Even week) and select it as the new Time Machine backup drive, will it start over from the begining again? Or will it recognize the past backups and do an incremental backup from there?

 

[Weaselboy]

Yes I know. But isn't there a way to do it manually? For example, Drive A as been my Time Machine drive for the past 7 days. if I connect disk B (which was used last Even week) and select it as the new Time Machine backup drive, will it start over from the begining again? Or will it recognize the past backups and do an incremental backup from there?

If you name the two drives the same, you can switch them back and forth. But there will big gaps in the backup sets. So if you backup both today, then backup disk one on Saturday... all changes between today and Saturday will be added to disk one. Then on Monday you backup again to disk two... it will only add things that were changed/added since Saturday and you would be missing data between today and Saturday on drive two.

Mountain Lion addresses this by recognizing two backups sets and knowing what to add to each.

 

[Jim_Lafleur]

If you name the two drives the same, you can switch them back and forth.

OK. What if we don't name them the same? And everytime we plug each drive, we go into Time Machine setup to select the "new" drive we want to backup to. Will it sync the changes since the last time? Or still leave a gap?

 

[Weaselboy]

OK. What if we don't name them the same? And everytime we plug each drive, we go into Time Machine setup to select the "new" drive we want to backup to. Will it sync the changes since the last time? Or still leave a gap?

If you name them differently, it will not be fooled into thinking you are using a the same disk, then will make a whole new backup each time. There just is no good way to do what you want with TM on Lion.

You could use Lion with TM for one backup disk then something like Carbon Copy Cloner to make the second backup disk.

 

[Jim_Lafleur]

You could use Lion with TM for one backup disk then something like Carbon Copy Cloner to make the second backup disk.

Good idea. I'll do that!

Thanks a bunch Weaselboy!