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I have TimeMachine disks for 2 Apple Silicon Macs [a macmini and a 14" macbook pro]. In the last couple of days both TimeMachine backups failed [supposedly due to lack of space] and the Time Machine Backups themselves have disappeared. Why?
MacBook Pro 14″, macOS 12.4
bankangde wrote:
... both of these Time Machines share space with a Copy Cloner backup. Under APFS there are two containers on each disc - one the CC backup and one Time Machine.
... If there was a fundamental problem in using only part of a disc for Time Machine, why has it worked well for so long?
Apple ( Types of disks you can use with Time Machine on Mac - Apple Support ) says you should reserve the entire disk for Time Machine. So using it also for CCC is probably a mistake, plus you now have both types of backups on the same physical drive so when that device fails, you lose all your backups.
"Note: The entire APFS volume is reserved for Time Machine backups. If you want to store files other than the Time Machine backup on the same physical device, use Disk Utility to create an additional APFS volume on the disk. The two volumes then share the available space."
Your setup with the containers and different types of backups on the same disk is not supported by Apple. I'm not surprised that the two types of backups have started to conflict. I suspect neither is a reliable backup anymore.
It might work for a while until one of the backups tried to reserve or use space that the other was using. We have no way of knowing without understanding the details of how CCC or Time Machine writes to different physical locations of the disk.
You should use one physical device for Time Machine backups and a separate physical device for CCC backups. If your backups are somehow compromised, that defeats the whole purpose of having a backup.
bankangde wrote:
... both of these Time Machines share space with a Copy Cloner backup. Under APFS there are two containers on each disc - one the CC backup and one Time Machine.
... If there was a fundamental problem in using only part of a disc for Time Machine, why has it worked well for so long?
Apple ( Types of disks you can use with Time Machine on Mac - Apple Support ) says you should reserve the entire disk for Time Machine. So using it also for CCC is probably a mistake, plus you now have both types of backups on the same physical drive so when that device fails, you lose all your backups.
"Note: The entire APFS volume is reserved for Time Machine backups. If you want to store files other than the Time Machine backup on the same physical device, use Disk Utility to create an additional APFS volume on the disk. The two volumes then share the available space."
Your setup with the containers and different types of backups on the same disk is not supported by Apple. I'm not surprised that the two types of backups have started to conflict. I suspect neither is a reliable backup anymore.
It might work for a while until one of the backups tried to reserve or use space that the other was using. We have no way of knowing without understanding the details of how CCC or Time Machine writes to different physical locations of the disk.
You should use one physical device for Time Machine backups and a separate physical device for CCC backups. If your backups are somehow compromised, that defeats the whole purpose of having a backup.
Time Machine backups will fail when the backup is larger than normal and the Time Capsule hard drive is close to being full.
But, we don't know if you have a Time Capsule. Might that be the case?
Time Machine backups "disappearing" is a separate issue. If you have a Time Capsule.......have you.....
If an error message appears, please post back with the exact text of the message.
I don't have a Time Capsule. I have two different SSD external hard drives with a 2TB section on each for backing up the respective Macs [1 2020 macmini; 1 2021 14" macbook pro]. Both worked flawlessly for many, many month until the last few days. For the mac mini I could see that before the most recent attempt at using Time Machine, the disc contained multiple backups, but afterwards in the finder no backups were present, even though only 7.6GB of space was available. Strange and distressing.
Very strange indeed. You did power off everything and restart again, correct? When you open Time Machine again, give the backups 10-15 minutes to load.
Regarding "Finder".......are you using the Mac's normal Finder function or are you using the Finder function that is built into Time Machine to navigate among the backup files?
If you try to run a backup, what if any error message appears on the Mac's screen?
Not only did I power off and restart again, but on the Macbook Pro I restarted in Safe mode with the same results. I tried looking at the backup discs in both Time Machine [where at first I could see the various backups but not navigate to them [all the rectangles next to the dates were in red] or not see them at all] and in the Finder [where only one data file was visible]. I just reattached the Time Machine backup disc to the Mac mini and 17 backups that go back to January do show up. I'm hesitant to try and backup things normally - should I delete one of the backups manually before retrying?
bankangde wrote:
I have two different SSD external hard drives with a 2TB section on each for backing up the respective Macs ... should I delete one of the backups manually before retrying?
You seem to be using Finder to work with these Time Machine backups. That's something that Apple advises not to do. If you have manipulated any of the folders or files on the backup drives used for Time Machine, that can throw Time Machine off and render the backups unusable.
Also you indicate that you have a "2 TB section" on the drive for backing up. Apple recommends dedicating the ENTIRE DRIVE to Time Machine and not using it for anything else. Have you been reading/writing to these drives for other purposes? Are these external drives APFS? What did you mean by a "section" - is that a container, volume, partition ... something else?
I'm not blaming you for any of what you experienced. However there are many postings in these Discussions from people whose Time Machine backups have been compromised because they used the drive for other things in addition to Time Machine, and also because they changed things on the Time Machine drives via the Finder.
Thanks for the note — I've been using Macs for decades and if this problem is due to me screwing up, it won't be for the first time! First, I only looked at the drives in the Finder after I had problems with the Time Machine backups. Secondly, you may be on to something as both of these Time Machines share space with a Copy Cloner backup. Under APFS there are two containers on each disc - one the CC backup and one Time Machine.
In any case, I've been using this system on the Mac Mini for about a year and a half and on the Macbook Pro for over 6 months and have had no problem with them until this past weekend. If there was a fundamental problem in using only part of a disc for Time Machine, why has it worked well for so long?
Thanks much. This appears to answer my question and it seems that I was just lucky for a period of time. For Time Machine backup I have not real need for speed. I hope that I am not out of line here, but do you think I could get away with using a HDD instead of a SSD for either backup or Time Machine with this Apple Silicon machines?
bankangde wrote:
Thanks much. This appears to answer my question and it seems that I was just lucky for a period of time. For Time Machine backup I have not real need for speed. I hope that I am not out of line here, but do you think I could get away with using a HDD instead of a SSD for either backup or Time Machine with this Apple Silicon machines?
Yes. I use an older 6TB OWC Mercury Elite Pro for my Time Machine backups.
bankangde wrote:
... do you think I could get away with using a HDD instead of a SSD for either backup or Time Machine with this Apple Silicon machines?
I use both SSDs and HDDs for Time Machine backups. With a USB-C/Thunderbolt or USB-3 connection, I see 500+ MB/s with SSD and 100 MB/s with a 5400 rpm HDD external portable drive. The first Time Machine backup is much slower with the HDD but subsequent incremental ones are acceptable. All these drives are on APFS, which is very non-optimal for HDDs, but is optimized for SSDs. See this article which explains why HDDs are so slow with APFS: https://bombich.com/blog/2019/09/12/analysis-apfs-enumeration-performance-on-rotational-hard-drives
Additionally, Time Machine will fail if there's not enough room on the boot drive to create a new local snapshot. How much free space do you have on the two boot drives?
On the Mac mini I have over 455GB of free space on the hard drive; on the Macbook Pro aoubt 150GB of free space. Should be enough, no?
Well, that shoots down another brilliant theory. 😢
Time Machine has stopped working May 2022
