External hard drive for iMac Time Machine
October 4, 2019 10:46 PM   Subscribe

I think I need to replace my 2TB Verbatim external hard drive, which I use exclusively for Time Machine backups on my iMac (Retina 5K, 27-inch, 2017) running MacOS Mojave 10.14.

This morning I received an error message: "macOS can't repair the disk "Samsung 2TB external. You can still open or copy files on the disk, but you can't save changes to files on the disk. Back up the disk and reformat it as soon as you can."

The drive is almost full, with 158GB available. Should I be looking at a 4TB drive? Or can I get another 2TB drive and dump the oldest backups? Time Machine does open and read the drive, but I'm not sure how to eliminate the oldest backups. I don't have anything large enough to back the disk up to, and I don't know if reformatting it will solve the problem.

Which drive should I get that will "just work" with my Mac and doesn't require reformatting before use?

I saw this and this, but they're probably out of date.
posted by Joleta to Technology (6 answers total) 1 user marked this as a favorite
Best answer: I have a WD My Passport 4 TB Portable Hard Drive. It will cost you a $100 from a well-known online retailer or $109.99 from Western Digital. It takes up very little space and works well.
posted by TheRaven at 12:51 AM on October 5, 2019 [3 favorites]

I use 2-4TB drives for backup on my iMacs and MBPs. I swap in a new one every year or so, even though they often aren't full. I usually get whatever is low (but not lowest) priced on Amazon. Brands I'd choose are WD, Seagate and Toshiba. I think there's only a few actual disk manufacturers, so brands other than those will probably have a WD, Seagate or HSBC disk in them.

I don't recall having to do a time-consuming reformat on anything in the past few years, but you may have to click through an "Initialize This Drive" screen.

You should definitely get a new drive started; once you start seeing "can't repair" messages, you're on thin ice and may not be able to get your information off that drive for much longer.

There may be a way to transfer e.g. the last few weeks of backup from your old drive onto your new one, but I've never done that. If you just start backing up onto a new drive, then obviously your Time Machine on that drive won't have the long back-history that your current drive has.
posted by spacewrench at 7:22 AM on October 5, 2019

Best answer: Time Machine should be automatically deleting old backups to maintain enough free space for new ones, which makes me think there's something wrong with this disk. I've only got 21 GB available on my 2-TB Time Machine drive and it hasn't been complaining.

It is possible to transfer a time machine backup, and with hard drives constantly getting bigger and cheaper, I'd get a bigger drive just on general principles. I'd get on that sooner rather than later.
posted by adamrice at 7:47 AM on October 5, 2019

Best answer: Another vote for Western Digital. I've got a My Book 4T; it stands vertically, which helps minimize the footprint on the computer desk.
posted by Bron at 10:17 AM on October 5, 2019

One more vote for WD. One word of warning: I copied everything from an old 2TB HD and it took a couple of days of running non-stop to finish.

I've used a 3 WD drives in succession over the years for TimeMachine, and have never had a problem. YMMV, of course.
posted by qurlyjoe at 11:18 AM on October 5, 2019

Response by poster: Thanks all. I bought a Western Digital 4GB My Book today and will follow adamrice's link to transfer my Time Machine backup from the old drive.
posted by Joleta at 2:21 PM on October 5, 2019

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