Time Machine's actions when assigned external disk is NOT connected

[hans_s]

I tried reading through existing posts regarding time machine but it's a daunting task so please forgive if this question has already been answered somewhere in the forum.
I want to use Time Machine irregularly to do a backup of my entire laptop at a specific time of my choosing. So it could be once a month or shorter or longer intervals. Time Machine seems like a better option than drag/dropping files manually every-so-often. However, Time Machine indicates that if my target drive is not connected to my laptop Time Machine will still take hourly snapshots and store it on my internal drive until the next time I connect the target drive. If I don't reconnect for a month or so that'll chew up a lot of my internal disk space! Does un-ticking the "Automatic Backup" disable this behaviour? I have done a lot of online search, reading and watching YouTube videos and no one addresses this. Thanks.

 

[Cougurr]

In my experience using Time Machine it will backup only to the "Select Disk" option you have selected when choosing your external hard drive. This can only be selected when connected to your laptop. So in my case on my 13" MBPro I have to remember to plug in the external drive when I power it back up for it to actually be able to do its backup. If I have it on without plugging it in, it does not do any backup function as there is no selected destination available, so it may give me a message that its missing but next time I do plug it in, the backup is updated on that date. If I have it on for a number of hours/days it does its hourly updates as usual. I have left the Automatic Backup option selected so that when I do plug it in and power on, it just does its update and continues along until I end my session of use on the MBPro. Then I check it is not doing a backup and do the "eject" of the external drive before, I shutdown the the computer. If you turn of this "Automatic Backup" option then it will not do any backup anywhere until you manually tell it to "back up now" by menu selection after you have connected your external drive.

I have never tried selecting the home drive of my laptop because the option for me has never been present. The list under "Select Disk" only shows external or network drives available for me. Perhaps someone else can comment on the message you are getting saying this is happening onto your internal drive.

I would suggest that you plug in your external drive and then go to this list to confirm that is the correct one selected by name. If not, then do select it and allow it plenty of time to either create a new backup or for you to confirm it has completed a current update before you "Eject" the external hard drive you are using.

For your desire to control when you do your backup's, I think switching off the "Automatic Backup" option might be a suitable option. Then you would only get a backup when you set it up to happen and tell it to"backup now" to your external drive.

 

[hans_s]

Thanks Cougurr that's how I'd expect it to work ... it makes sense and I am just going to have to try it. I have never used time machine before so I did a lot of online reading and that's where I read this that if you disconnect the target drive so that time machine can't find it for backing up, then snapshots will be stored on the internal disk until the target disk is reconnected at a future date. But it didn't say anywhere that if you don't want this action then deselect the Automatic Backup option. Anyhow, thank you for replying back ... much appreciated.

 

[Cougurr]

Your welcome Hans. I forgot to mention that you can point to more than one target location, On two of my machines I have them alternate between their external HD and a network HD. After you have selected the first external drive of your choice and have it running then if you select a different one it will ask you if you want to stop backing up to the first one or alternate between the two. I made the choice to go to both and that way if one or the other backup hard drive fails then I still have a backup of the computer.
Colin

 

[chas_m]

1. The ”snapshots” are just lists of files/folders that need to be changed when the Time Machine drive is again connected. They don’t take up much space, so that’s not a concern.

2. Time Machine is designed to be a “set it and forget it” solution, so the best way to use it is to have a self-powered external drive connected to it pretty much all the time*. Using it for irregular backups makes Time Machine more complicated to use, and creates big gaps in the “timeline” when you are trying to regain a document that was accidentally deleted. Long gaps between backups of course create many more opportunities to lose documents that cannot be regained, or not regained in the version you need.

*you would of course eject and unplug the drive when taking the laptop elsewhere, but Time Machine will just do another backup as soon as it is reconnected to the external drive.

3. If you still want to make irregular backups, my suggestion would be to use a program for backups that is schedule-able. Chronosync, Carbon Copy Cloner, and Super Duper are all options to consider. There may still be a program called Time Machine Editor out there that makes Time Machine schedulable — but IIRC if you set a schedule for irregular backups, that drive better be connected when the schedule is ready!