I noticed that this question was asked before, but the answers came from other community members and not from an Apple tech. All the answers seemed to be educated guesses, but no one actually seemed to be able to answer the question.
Any new information?
MacBook Air, macOS High Sierra (10.13.4)
Thanks JimmyCMPIT, but I was hoping that someone may have gotten the answer elsewhere and would have been able to answer.
Found something at a place called PressReader:
"...When preparing to back up, Time Machine doesn't check every file and folder to see if they've changed since the last Back Up. Instead it relies on a record of file system events named FSEvents, which saves a lot of time and effort. Sometimes, FSEvents can become wobbly or missing, in which case Time Machine will perform a 'deep event scan' of its own, which can take an hour or more. You can invoke it manually by opting for the 'consistency scan'."
That helped a lot-as well as answering the question as to why 'Preparing Back Up' may sometimes take far longer than usual.
Matt
Thanks JimmyCMPIT, but I was hoping that someone may have gotten the answer elsewhere and would have been able to answer.
Found something at a place called PressReader:
"...When preparing to back up, Time Machine doesn't check every file and folder to see if they've changed since the last Back Up. Instead it relies on a record of file system events named FSEvents, which saves a lot of time and effort. Sometimes, FSEvents can become wobbly or missing, in which case Time Machine will perform a 'deep event scan' of its own, which can take an hour or more. You can invoke it manually by opting for the 'consistency scan'."
That helped a lot-as well as answering the question as to why 'Preparing Back Up' may sometimes take far longer than usual.
Matt
You may find the following article an interesting read:
Watching macOS file systems: FSEvents and volume journals - The Eclectic Light Company
In addition, if you want to "watch" a Time Machine backup in progress, you can use the following Terminal command:
sudo fs_usage -f -R filesys backupd
If you want to check for potential process errors, use this command instead:
sudo log stream --predicate 'subsystem=="com.apple.TimeMachine"' --info
There are no Apple "techs" on a user-to-user support forum, so you might want to contact Apple directly to confirm that Backup with Consistency Scan combines two separate actions.....Verify Backup and Backup Now into one process, although Verify Backup actually involves several different processes, as does Backup Now.
This is a volunteer forum. To speak directly with Apple call 1-800-MY-APPLE or go to apple.com/contact for a list of international phone numbers.
What is a BackUp with Consistency Scan?
