Time Machine Forgets Backup Disk

Question

Time Machine Forgets Backup Disk

For years, I have used an external drive as a Time Machine backup. I don't leave it on all the time: At night I turn everything off and unplug my computer because I'm paranoid about power problems.

When I want a backup, I plug in the Time Machine disk and let the system do its thing.

I've never had a problem until after upgrading to Lion and switching to a new backup drive. As always, I partitioned the Time Machine volume as one large GUID volume. I went into my Time Machine preference pane and selected the new disk to be used as the Time Machine volume, and let it rip. It performed a full backup of my system, and then a couple of hourly backups over the course of the day.

The next time I turned on my computer, I did not plug in the TM volume's disk drive. When it came time for a backup, Lion couldn't find my backup volume, so it automatically switched to my internal hard drive as the backup volume! It then presented me with a scary warning that the backup volume changed since the last backup, saying somebody might be trying to trick me, and giving me the option to continue or stop the backup. Of course I stopped to investigate and found that it intented to fill up my internal drive with a backup copy of the same drive!

No matter how many times I mount the desired TM volume and re-select it and performed a backup -- which is always successful -- whenever the system can't find the real TM volume, it forgets it and tries to back up to the internal hard drive and I get the scary warning again.

I already tried deleting my Time Machine plist file and starting from scratch, but the problem recurs every time. To prevent the warning (and prevent Time Machine from filling up my internal drive), I've had to disable Time Machine altogether.

Does anyone know of a permanent solution to select one single backup volume and have Lion respect that choice, without automatically switching to the internal drive whenever there's a hiccup?

Answering that I shouldn't shut down, or that I should always leave the TM volume running won't be helpful. In previous versions of OS X, Time Machine always delayed backups until the volume was available. All I want to do is return to that proper behavior.

iPad, iPhone, iMac, MacBook

Posted on Jun 20, 2012 8:23 PM

Reply

Answer 1

Jun 21, 2012 10:29 AM in response to Charles Jenkins1

I don't have a direct answer to your questions, but you might find useful advice on these Web sites:

Time Machine FAQs

Time Machine Troubleshooting

As you've discovered, under Lion Time Machine on a portable Mac tries to keep backups on the local disk if the Time Machine disk isn't available. Those resources should explain that in more detail.

Reply

Answer 2

Pondini

Level 8

38,863 points

Jun 21, 2012 4:01 PM in response to Charles Jenkins1

Charles Jenkins1 wrote:

. . .

When it came time for a backup, Lion couldn't find my backup volume, so it automatically switched to my internal hard drive as the backup volume!

Yes, a (very) few other folks have reported that. Nobody seems to know just what's wrong, much less a confirmed way to fix it.

It sounds like something corrupted in your installation of OSX, but:

One user reported that reformatting the TM drive and doing a "full reset" of Time Machine, per #A4 in Time Machine - Troubleshooting fixed it.

Another switched to a different backup drive, and that fixed it.

(Neither of those make any sense to me, but you never know.)

The only other thing I can suggest is to try installing the "combo" update, per Installing the ''combo'' update and/or Reinstalling OSX. If that doesn't help, installing a fresh version of OSX (that won't disturb anything else), per the same article, might help.

Reply

Answer 3

Jun 21, 2012 7:33 PM in response to Pondini

Mr. Jenkins wrote "The next time I turned on my computer, I did not plug in the TM volume's disk drive. When it came time for a backup, Lion couldn't find my backup volume." That sounds to me like expected behavior, at least at that point. However, that alone doesn't explain why he couldn't select the real Time Machine disk later. Is it possible that he has a "phantom volume" in /Volumes?

Mr. Jenkins, if you dismount that Time Machine disk, invoke the Finder menu option Go > Go to Folder, then type "/Volumes" (without the quotes) in the field and click "Go", do you see anything like your Time Machine disk in the resulting window?

Reply

Answer 4

Pondini

Level 8

38,863 points

Jun 21, 2012 7:42 PM in response to William-Boyd-Jr

William Boyd, Jr. wrote:

Mr. Jenkins wrote "The next time I turned on my computer, I did not plug in the TM volume's disk drive. When it came time for a backup, Lion couldn't find my backup volume." That sounds to me like expected behavior, at least at that point.

But he also wrote: "so it automatically switched to my internal hard drive as the backup volume!"

I assume he means, it actually put his internal HD on the TM preferences panel as the backup disk. That's not going to /Volumes because it lost track of the drive, it's going to a Backups.backudb folder at the top level of the internal HD. We've seen that posted by 2 or 3 other users.

I also suspect it's the cause of the folks who couldn't upgrade to Snow Leopard or Lion, with the message about it being a Time Machine volume. Those also had a Backups.backupdb folder on their internal HDs. Several had only a single internal HD with one partition, and no external clones, so could not have selected their internal HD by mistake.

It's rare, but something's doing this on occasion.

Reply

Answer 5

Jun 21, 2012 7:48 PM in response to Pondini

Pondini wrote:

I assume he means, it actually put his internal HD on the TM preferences panel as the backup disk.

That should be easy to verify. I'll defer to your greater Time Machine expertise.

Reply

Answer 6

Jun 22, 2012 10:13 AM in response to Pondini

Pondini wrote:

I assume he means, it actually put his internal HD on the TM preferences panel as the backup disk. That's not going to /Volumes because it lost track of the drive, it's going to a Backups.backudb folder at the top level of the internal HD. We've seen that posted by 2 or 3 other users.

Yes, that is exactly right. In the interest of keeping it brief, I didn't write about what happened when I accidentally clicked the button on the scary dialog that allowed the backup. At that point, TM created a Backups.backupdb folder on my internal drive and changed its icon from the pic of an internal drive to the Time Machine Volume icon. I killed the backup before it started copying into the Backups.backupdb folder, deleted that folder, deleted my TM plist files, and rebooted in order to get the proper icon back -- which assured me that the internal drive was no longer configured to be the TM volume. Then of course I went through the cycle of plugging in the real TM volume, re-selecting it in the TM pref pane, and allowing a backup to it. Everything worked great -- until the next time the TM volume wasn't available at backup time.

I'm not in front of that Mac at the moment, but I will try the resources you've suggested when I can.

Reply

Answer 7

Jun 22, 2012 10:19 AM in response to Pondini

Hmm. It seems the Time Machine Full Reset basically means to remove the plist file and reconfigure, which is what I already tried.

I suspect I need to try the procedure to reinstall Lion.

Reply

Answer 8

Pondini

Level 8

38,863 points

Jun 22, 2012 10:27 AM in response to Charles Jenkins1

Charles Jenkins1 wrote:

. . .

TM created a Backups.backupdb folder on my internal drive

You'll want to delete that. It's presence will keep you from upgrading OSX.

Reply

Answer 9

Pondini

Level 8

38,863 points

Jun 22, 2012 10:33 AM in response to Charles Jenkins1

Charles Jenkins1 wrote:

Hmm. It seems the Time Machine Full Reset basically means to remove the plist file and reconfigure, which is what I already tried.

Yup. 😟

I suspect I need to try the procedure to reinstall Lion.

Are you covered by AppleCare? If so, you might want to call them before doing anything else. That way, they can get engineering to work on finding the cause. We don't even know if they're aware of it.

It might be worthwhile just installing the "combo" update first (much faster and easier).

Reply

Answer 10

km_foto

Level 1

0 points

Nov 5, 2013 9:01 AM in response to Charles Jenkins1

I have the exact same issue, did you ever solve yours? Is simply using another hard drive the only way?

Reply

Answer 11

Nov 6, 2013 10:56 AM in response to km_foto

km_foto,

I'm sorry to say I soon gave up using Time Machine to backup that particular iMac. When I want a backup, I plug in the drive and turn Time Machine on, and when the backup is done, I turn Time Machine back off.

TM seems to be riddled with bugs and issues. My home network has a Time Capsule that I can use as a data drive all day long, but I can't use it as a Time Machine backup disk for my Macbook Air. I can do one successful full backup to it, then the next time TM tries to run, it dies with an error saying it can't connect to the disk. I have to delete it from my list of TM backup drives, then re-add it and re-input the password, then TM does a lonnnnng full backup to it--and an hour later dies with the error again. I gave up and bought an external drive to backup my laptop.

At work I updated to Mavericks and my first TM backup wiped out all the old backups of files in my main account but left other accounts alone. Fortunately I copied most of my important data over before TM ran that backup, so the only files lost forever were ones that had been left sitting on my Desktop.

I think moral of the story is, don't trust Time Machine as your only backup solution.

Reply