As one of my backup solutions, I use an app (SuperDuper!, if it makes any difference) to make a clone of my Mac at the same time every evening. Sometimes I am still working at that time. What I want to know is: should I stop using my Mac while the clone is in progress? Why or why not?
Intuitively it seems that if a file is being modified while it is being copied to the clone drive that could affect the integrity of the backup. However, it would be good to have a definitive answer from someone who knows.
Thanks for reading.
Best Answer
Your instincts are correct.
If a file is being modified when the program reads it, you will end up with a copy of it in a transient state (or perhaps some programs like iPhoto that have a database that tracks files - the structure might not be correct to run with after a restore.)
This is why Time Machine makes two passes - it copies everything and then runs a second copy to pick up any files that were in the process of being modified during the first pass. Of course, a file under constant change might not get saved in either case, but it reduces the odds of a critically vital file that doesn't get changed often will be caught in a delicate moment.
To be safe, you want to boot to another OS (the recovery HD or an external drive) to run imaging if you need to ensure a perfect copy and all files being closed and flushed properly to storage.