Upgraded to Catalina; Time Machine backup failed

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Upgraded to Catalina; Time Machine backup failed

I am no longer able to back up my files via Time Machine onto my external storage. This happened right when I upgraded to Catalina, and (if I recall correctly) it happened the last time I upgraded my OS as well. I am using an iMac Retina 21.5", fairly new.

Usually, Time Machine automatically deletes old files to make room for new ones, but now I simply get a "Backup Failed; There isn't enough space on "(external HD)".

I see lots of advice on how to delete just one or two files to make room, but will that work? Do I have to delete everything now? Is it a problem with the new Catalina upgrade?

iMac 21.5" 4K, macOS 10.15

Posted on Nov 14, 2019 1:41 PM

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Answer 1

Top-ranking reply

rkaufmann87

Level 10

144,054 points

Nov 14, 2019 2:43 PM in response to andreafromhilo

By chance do you use a NAS device for Time Machine? If so, please check with the developers of the NAS device about their plans to support Catalina.

However, if you are not using a NAS and you are getting the "Backup Failed; There isn't enough space on "(external HD)". error, you will need to re-format and start over or you can get a larger capacity EHD and migrate your TM backup to that and pick up where it left off. I have done this several times and have use Apple's instructions in https://support.apple.com/en-us/HT202380

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Answer 2

den.thed

Level 10

82,528 points

Nov 14, 2019 2:59 PM in response to andreafromhilo

I was thinking along the same lines as rk87. If your TM backup drive was nearly full and thinning old backups, then it just doesn't have or think that there is enough room for the first new Catalina backup.

So on that note, you have few options to carefully consider.

Move the current set of backups to a larger external backup drive.
Set the current backup drive aside and buy/use another backup drive for Catalina.
Erase the current Time Machine backup drive and start with a new set of Catalina backups.

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Answer 3

Nov 14, 2019 5:13 PM in response to rkaufmann87

I am not using an NAS device. My Time Machine backs up to a La Cie external hard drive.

How do I reformat and start over? I know that will erase all my back-ups. I am recalling that, when my previous iMac died and I got this new one and a new OS, TimeMachine had to be erased and I had to start over (but the Mac shop did that for me.)

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Answer 4

Nov 14, 2019 5:19 PM in response to den.thed

den.thed, I am thinking I need to do #3, but I'm not too sure how.

Is there something about Catalina which would prevent me from deleting just part of my current backups, making it unnecessary to erase the whole backup? That is, say I erased enough backups to that it started backing up automatically again; would I be able to read/access/use the pre-Catalina backups?

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Answer 5

den.thed

Level 10

82,528 points

Nov 14, 2019 8:13 PM in response to andreafromhilo

Sorry I had to be away for awhile and glad to see that your follow up question was answered.

Your TM backup drive should be 2 to 3 times larger than the data you have on your internal drive.

For example's

If you had around 150GB of data on your internal drive, then your 500GB external drive would allow for backups, plus a little additional space for new data growth on your internal drive.

If you had around 300GB of data on your internal drive, then a 1T external drive would allow for a greater number of backups, plus additional space for new data growth on your internal drive.

500GB on the internal drive, then a 1.5 or 2T external drive and so on.

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Answer 6

Bruce W

Level 1

38 points

Dec 20, 2019 12:58 AM in response to andreafromhilo

I have the same issue. I do not back up to a NAS drive but an USB3 SS external drive. This was the same drive I used before the Catalina upgrade without issue. I even wiped by backup drive and started again from scratch but the issue came back.

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Answer 7

rkaufmann87

Level 10

144,054 points

Nov 14, 2019 5:44 PM in response to andreafromhilo

Go to Disk utilities , format the drive and assign it as your Time Machine drive.

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Answer 8

Nov 14, 2019 6:17 PM in response to rkaufmann87

Thanks, I found Disk Utilities and the "erase" button. FYI, my LaCie is 500GB. Some of the previous advice was to get a larger external HD. Is 500GB generally considered insufficient?

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Upgraded to Catalina; Time Machine backup failed

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