Time Machine conflict

My Time Machine EHD purchased when I bought my Mac is a SeaGate Backup Plus. Recently, I needed to buy an additional EHD to back up my files on my Mac. It is also a SeaGate Backup Plus. When not wanting to backup the Time Machine, I leave it unplugged. But now my Time Machine sees the new EHD as a way to back up. And I get the message "backup failed". How do I resolve this conflict? Thank you in advance for any help you can provide.

Too little information to really know. What Mac? What version of macOS? Are you leaving TM running, active, but just disconnect the drive? If you are doing that, then what TM is doing is making temporary images on your internal drive until it gets the backup drive again. That's not really how you should do that. It may be that when you then connect another drive of exactly the same name (my assumption for that), then TM sees it and wants to use it. But the backups are not there, so the backup "fails" for lack of previous backups being there to add the temporary snapshots to it.

So get us more information. Also look into something like Time Machine Scheduler or Time Machine Editor to put your backups on a longer interval and try to leave the TM drive attached so that when the interval arrives, TM can do the backup. I use TME and do backups twice daily, noon and midnight.

MacBook Pro, MacOS High Sierra, latest update. Yes, TM is running, active but disconnected the drive. Yes the new EHD is exactly the same name as the one that I use with TM. I would like to make a longer interval, so I'm not sure how to do that. I entered TM and didn't see that option. Also, is there a way to delete the oldest backups automatically. Thanks again for your input.

OK, thanks for the information. The short answers are that it would be best to rename the new drive to something different to keep from confusing TM. TM backs up every hour by default, can't be lengthened, but can be shortened. It also deletes old backups automatically for you, you should not touch them with Finder or any other tool.

Now, the longer answers. At the first backup TM backs up everything. That is the base backup. After that, it only backs up things that changed since the last backup, called an incremental backup. When you look at the backups in TM, it looks like all the files are there in each backup, but all that is there is a special kind of link to the last time the file changed. That link may go back 1 or 2 or 3 or 50, or more, backups (maybe even all the way to the base backup if the file never changes). If you reach in with Finder to do something, you can break the linkage and destroy the integrity of the backups. TM files should ONLY be touched by TM itself because when it manipulates the files, it fixes the links as well. When TM runs out of drive space, it will delete the oldest backups first, either notifying you or not, depending on your settings. When the backup drive is absent at the time of a backup, TM takes a "snapshot" of the drive and stores it on the drive itself as a holder, waiting for the backup drive to be reattached. When you attach the new drive with the same name, TM looks for its files, doesn't find them and errors out. When you connect the right drive, it finds the folders it's looking for and proceeds. If there are snapshots, it puts them into the backup, then erases them from your internal drive. On a restore, you pick the time you want to restore to, TM then checks that the file(s) you want restored are either actual files or links, follows any links back to the unchanged version of the file and restores it for you. It depends on that database integrity for that to happen.

What TimeMachineScheduler and TimeMachineEditor do is allow you to set a longer interval between backups. They way they work is that you leave TM OFF, but the drive attached. At the interval you set, they start TM, do a backup and then turn TM off again. If the backup drive is not there, TM will just do what it does, make a snapshot.

EDITORIAL: Snapshots are, to me, pretty useless. If your drive fails, you lose them. If you need the data, keep the backup drive attached. An unfinished backup is not much good if the drive fails.

So, it's up to you what to do. If your data is critical and time sensitive, you may need to backup every hour or more frequently. I don't need that, so I set mine to noon and midnight. I'm thinking of going to just midnight, but just haven't gotten to that yet. TMS and TME both run in the background, wake up TM at the right time, run it, then turn it off again, all automatically. As I said, I use TME, have done so for a long time and it works well for me.

What I used to do with my MBP, I would turn Time Machine off, then disconnect the drive. When I wanted to backup, I would connect the drive, and turn TM back on again.

The short answers are that it would be best to rename the new drive to something different to keep from confusing TM.

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Actually the renaming would be a good idea for the benefit of the user and save them from any confusion.

All Operating Systems use a Volume ID of a hard drive which actually uses a Unique Identification System that keeps all drives as unique.




- Patrick
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But you tell TM what drive to use by NAME, and then it looks for that name. Similarly named drives can confuse it. I've had that happen before. I know it SHOULD use VID, but it apparently does not.

Bob, I did the manual on/off thing until I found TME. Then it seemed just easier to let the computer do what computers do best, that is, to remember and execute mindless tasks for me. I could never remember on a faithful schedule to make that backup. Since I am one of those who has experienced a drive failure and a simultaneous drive failure of the backup drive, I now have multiple backups, all on automatic schedules.

So, do I rename that Time Machine drive the same way I would rename any file or folder? Also what is TME and how do I execute it? You guys are great with answers. So appreciate all the input.

Don't rename the TM drive, rename the NEW drive to something other than the one it is now. You can do that by right clicking on the drive, then Get Info and rename it there. It may require you to unlock the padlock on the bottom of the Get Info window to rename it.. TME is Time Machine Editor, a third party app you can search for and get from the developer.

But you tell TM what drive to use by NAME, and then it looks for that name. Similarly named drives can confuse it. I've had that happen before. I know it SHOULD use VID, but it apparently does not.

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Interesting Jake, and yes it should. And add another reason to my list for not using TM for anything critical.



EDIT:
According to Pondini who used to be an excellent/knowledgable Mac tech years ago says:

It's not the name, it's the UUID (Universally Unique Identifier) that OSX and Time Machine use to keep track of volumes

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https://discussions.apple.com/thread/2654125

It's the same thing that "CCC" does.




- Patrick
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That was ten years ago. Things change. This seems to be one. All I know is that TM can, and does, get confused if you replace one drive with another of the exact same name and it cannot find backups.backupdb on the drive. As for using the UUID, almost no applications use the UUID that I can think of. If you change the path name of a file by changing the drive name the application cannot find the file, even if the UUID is unchanged. So while UUID may be used by the OS at mount to establish a different mount, the bottom line is that from then on TM appears to use the path name for the backup files. (And CCC gets lost with different drive names, too. I have it and have to keep the path names consistent or it errors out for not finding the drive.)

The Pondini site has closed, sadly, there was a lot of great information there.

As for using the UUID, almost no applications use the UUID that I can think of.

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I know for a fact that CCC definitely does.
And an interesting comment at his site states:

it is statistically more likely that CCC's discovery of a duplicate UUID is due to a hardware or software problem rather than to two volumes randomly having the same UUID.

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It's also interesting where it doesn't seem to work as well:
https://apple.stackexchange.com/que...ount-disk-by-uuid-or-label-in-os-x-el-capitan


Yes, it's too bad about Pondini and his kaput Pondini site that someone was keeping alive for quite a while, but I believe it's archived somewhere and still available but getting somewhat dated by now.

Anyway, whether the Mac uses the hardware UUID/VolumeName or not, I'd say it's certainly best for the user at least to use separate volume names just to save confusion in their own mind.

Personally the same goes for a small home network and change things if any sharing etc. is done so that every Mac's drive isn't called "Macintosh HD".





- Patrick
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From the CCC help files at the website:

By default, CCC uses the name and Universally Unique Identifier (UUID) of your source and destination to positively identify those volumes. By verifying both of these identifiers, there is less risk in, for example, backing up to a volume that has the same name as your usual destination but is not actually the destination.

While beneficial, this behavior can sometimes have the wrong result. For example, if you rotate between a pair of external hard drives, CCC will not backup to both of them even though they have the same name (e.g. Offsite Backup). CCC will instead claim that the UUID of one of the volumes does not match that of the originally chosen destination.

To accommodate a "rotating pair of backup volumes" solution, you can uncheck this option to indicate that CCC should only use the volume name to identify the destination volume. When deselecting this option, be vigilant that you do not rename your destination volume and that you never attach another non-backup volume to your Mac that is named the same as your destination volume.

This option is automatically disabled when the destination volume does not have a UUID. Network volumes and some third-party filesystems, for example, do not have volume UUIDs.

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So CCC does, by default, use the UUID but with caveats and a user option to turn that off. And networked drives without UUID get treated as just named drives by default, along with drives formatted other than for macOS. I wonder if it does that if the internal drive is APFS but the backup target drive is HFS+? Be interesting to know for sure, but not critical to operating the software.

I have experienced drive issues with TM before and I have successfully cloned a dying TM Backup drive to a different drive and just replaced the failing drive with no protest from TM by giving it the same drive name. So TM either doesn't care about UUID, or is just happy to find a backups.backupdb to use at the path it was given to use. For networked drives, TM completely changes the backup to sparcebundle, so that's a whole separate approach to the drive situation.

So, it would seem that SOME things use UUID, and some things don't. Nothing constant in the world of computing, ever.

This is good information, but I still do not know how to change the backup intervals for the TM, since it looks like the website for downloading that has gone away. Any thoughts on how to do this another way?

And to clarify, with one of the above posts; I can right click on the new drive and give it a unique name, different from the TM backup. It's that simple?

Here is the website for TME. It's not gone away. https://tclementdev.com/timemachineeditor/

Yes, that is all it takes to rename the drive. Just be aware that if you used that drive to save any files from inside any apps, they may not be able to find the files because the path to them has changed. You'll have to open the files with the app again and save it again for the app to remember the new path.

Thank you for that info. I use Adobe Lightroom, and my LR files are saved on the EHD, so do I understand that I need to go through Lightroom to change the EHD name?

No, change the name as you described earlier, through the operating system. Then in Lightroom, if you try to open something from the history that is on the drive, LR won't find it because the path has changed. You'll have to manually find the files, open and close them again and the history in LR will be updated to the new path name.

So, it would seem that SOME things use UUID, and some things don't. Nothing constant in the world of computing, ever.

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Ain't that the truth Jake, ;D and I just chuckle to myself and sigh when I read that so-an-so has implemented a new "Standard" that is then seldom used or isn't even compatible with anything else!!! Sighhhh…




- Patrick
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I downloaded this program, and it seems to work the way you describe. MUCH easier than renaming a drive. I will just leave TM EHD plugged in all the time and it will back up when I've set the editor to do that. Thank you.

MacInWin said:

Here is the website for TME. It's not gone away. https://tclementdev.com/timemachineeditor/

Yes, that is all it takes to rename the drive. Just be aware that if you used that drive to save any files from inside any apps, they may not be able to find the files because the path to them has changed. You'll have to open the files with the app again and save it again for the app to remember the new path.

Click to expand...