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corby 03-07-2008 03:04 PM

TM and SD simultaneously backing up the same file

I'm a new Mac user and just started using both Time Machine and SuperDuper.

I read the FAQ and sucessfully did a Time Machine backup and a SuperDuper backup "along side" the Time Machine backup. So far, so good.

I'm using a MacBook, so during day to day use, it won't be connected to my external backup drive.

My plan is to connect to the drive periodically to do my backups (a few days per week).

I also use VM Fusion, which creates pretty large virtual machine files.

My question is this:
When I connect to the external backup drive, will there be any problem with Time Machine and SuperDuper both doing their backups simultaneously?

I'm concerned that the large files created by VM Fusion will take time to backup, and it might be the case where both programs will be trying to access those files at the same time.

Note: I've read from a number of sources that it's a good idea to exclude some large files from Time Machine, especially if they're frequently updated, because TM will need to make a new copy every time it does it's backups. (and manually back them up periodically).

I'm really not concerned about that because I won't be always connected to the drive, so I won't be backing up a new copy every hour, and I do want that file to be backed up whenever I do a backup.

So, do you think there will be a problem if TM and SD try to backup the same large file at the same time?



dnanian 03-07-2008 04:14 PM

Shouldn't be a problem, Corby (as I recall, TM doesn't back up your Fusion files). Note that when you run SD!, you should quit Fusion -- you don't want its images to be open when they're copied.

corby 03-07-2008 09:13 PM

I don't think TM excludes the Fusion files by default. For the time being, I have manually excluded the VMFusion files from Time Machine, just to be safe. On a desktop environment with backups occuring every hour, I could see where hourly copies of that file would use alot of disk space.

However, I would like to have TM backups of the Fusion files (in case I break XP!) and was planning to "unexclude" them, particularly since I would only be updating the backups once per day at the most.

So are you saying it would be OK if both TM and SD were making backups of the same file at the same time? (I will certainly close out of Fusion before hooking up the external drive)


dnanian 03-07-2008 10:17 PM

Yes, that would be fine, but having TM back up Fusion is not a good idea, since it'll keep a lot of copies of the VM and would run out of space rather quickly.

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