The built-in Time Machine backup function of Mac computers is really convenient to use. However, many people are actually not clear about some of the key details and limitations. This situation is very likely to cause the backup effect to be compromised, and even lead to the risk of data loss.
Startup timing and initial backup
It is recommended to turn on the time machine immediately when the new machine is set up, or after a system reinstallation. Because the first backup is generally a full disk copy operation, at this time, the system appears clean and contains the least number of files under one's name, so the backup is completed the fastest. If you start Time Machine after using it for a long time, the accumulated data will make the first backup take a long time, sometimes even several hours.
It is best to use an external mobile hard drive or network storage as the backup medium. Make sure that the capacity of the storage device is at least twice that of the Mac's internal hard drive, so that a sufficient number of historical versions can be retained. After connecting the device, the system will generally prompt whether to use it as a Time Machine backup disk.
Backup mechanisms and hard links
Time Machine uses an efficient storage method. For files that have not been changed between two backups, it does not store a copy again on the backup disk, but creates a "hard link" pointing to the original backup file. This is essentially the same file entry and does not occupy additional disk space.
The advantage of this mechanism is that it saves storage space to a great extent. When you restore the system or search for old files, Time Machine will display the file versions at all points in time. However, the underlying storage is shared. Only when the file content changes, the new data blocks will be actually written to the backup disk.
File deletion and pointer cleaning
In the Mac system, there is a situation where one file corresponds to multiple hard link pointers. Backup files generated by Time Machine have such pointers. If you only want to delete the file version at a certain point in time, just operating in the Time Machine interface may not be enough.
In an effort to remove all traces of a device from the backup, make sure you erase all hard links to it. Otherwise, the device data may still occupy the space of the backup disk. You can use terminal commands to find and control the device's reference count, but for most users, just use the delete function of Time Machine.
System crash and data recovery
If the Mac system fails to start normally, or a serious error occurs, the value of Time Machine backup will be highlighted. You can enter macOS recovery mode when restarting and choose to restore from a Time Machine backup. This process restores system files, applications, and user data to the state they were in when backed up.
It should be noted that the recovery behavior has the nature of overwriting. If the newly generated files and data since the backup time point have not been specifically backed up, they will be lost after the system is restored. Therefore, you should try your best to understand the timeliness of the backup before restoring.
Backup frequency and data security
By default, Time Machine automatically performs backups every hour, which raises a potential risk: if you create an important file between backups and then accidentally delete the file, the file may not have been backed up and cannot be retrieved.
In order to reduce such risks, for files that are particularly important or are being processed, it is recommended that you develop the habit of manually saving files at any time, and temporarily use the "quick backup" command to force Time Machine to immediately perform a backup-related operation, and do not rely entirely on the automatic cycle.
Partition restrictions and startup features
Time Machine is mainly designed to back up the boot disk, usually Macintosh HD. For other partitions that you have divided on the hard disk, Time Machine usually does not automatically cover them. If you have data stored in non-boot partitions, you have to manually add these partitions to the backup list in Time Machine settings.
What the bootable system disk cannot be is the Time Machine backup disk itself. It does not store the complete system installation image, but the data package used for recovery. To create a bootable installer, you need to use Disk Utility or the Create Installation Disk command.
During the use of Time Machine, after reading these specific points about Time Machine, what is the most unexpected backup or recovery experience that you have encountered? If you find it useful, please give it a thumbs up and share your stories in the comment area.
