Ah, I see. Basically you're saying I simply wipe the drive, then reformat it with the latest Mac filing system. Will that also allow it to connect to Windows computers, if needed?
Yes, that's what I'm suggesting. You posted above that the Time Machine (TM) drive is formatted "Mac OS Extended (Journaled)" (that's the same as what I called HFS+). A TM backup in this older format uses "hard links" to directories and files that exist in previous backups, in order to present an entire-disk view of each backup and not have to have multiple copies of those directories and files. My hypothesis is that after 10 years, there are so many of these hard links in the volume's filesystem that it takes a "long time" for the HDD to follow them (and add another link) on each backup, making the backup slow. (We don't have real solid evidence that this is the cause, though!)
A fresh, new TM backup disk would be (must be) formatted in the newer APFS format. Although APFS has some issues with HDDs, APFS has a feature called "snapshots": a much more efficient way to present the entire-disk view of old backups. It shouldn't get bogged down with multitudes of links to individual folders and files, even after years of use (by my understanding).
Many posters will argue about how it's "bad" to use APFS with HDDs. They are usually talking about potential fragmentation of the files that are modified, spreading parts of them around on the HDD and impacting performance. IMHO this is not a big problem with TM backup drives, as the vast majority of files are never modified. If it does severely impact performance someday in the future (like, years from now), my solution is to just wipe the TM drive and start again. (My policy is not to use TM backups as "archives" of stuff I *might* want in the future. If I think I might want it, I don't delete it from my main drive(s)!)
Anyway, for a new TM backup, macOS forces use of APFS, so you don't have much of a choice.
What do I do with the other data I've saved over the years through simply copy-paste (pictures, books, audio files)?
Very important: you must copy this data somewhere else if you decide to start a fresh TM backup! If I remember correctly, a new TM backup will use the entire disk (partition) and won't allow you to store other files on the TM volume.
Does this "other data" exist somewhere else already? Ideally, it should
not exist only on the TM drive. If the backup drive fails, you've lost your only copy! Ideally this "other data" will be on another drive (e.g., a different external drive) AND you would set TM to backup that external drive to your TM drive (in addition to your internal drive).
If "other data"
is only on the TM drive, I have a suggestion:
get a new 1TB external and use it as the new TM backup drive. Use your existing Seagate TM disk for the "other data", only. Set TM to include the older Seagate in backups to the new external. This way, if your 8 year old Seagate fails, all the "other data" will be available on the (newer) backup drive.
You're so right. I am not likely to go back to those old backups. But it feels strange to wipe out that older part of your life now that it's there is some form. Plus, who knows I may just end up needing to go back to those files for some unknown issue that crops up in the future 🙂
Yes, I understand. It's possible you'll want something from it in the future. If you're able to follow my suggestion above, you can retain the old backups (on the "other data" drive). You don't need to use Time Machine to access files in the old backups. Also, you could delete all backups older than, say, three years, to free up more space on the "other data" drive. (Don't try to backup the
old backups, though! If you keep them, you will probably need to add Exclusions to the TM settings.)
Sorry to be so long-winded! Sometimes I go a little overboard. : )
I do want to emphasize that this is what
I would do, but since we don't know for sure what's causing your extremely long backups, I cannot guarantee that starting a fresh TM backup would solve your probelm. Just that
I would try it. It seems pretty easy, to
me, and worth a try. If a fresh new TM disk was still so slow, I would replace the drive.
It could well be that the old HDD is starting to fail, and is causing slow reads and writes. Unfortunately, if the external HDD is conected via USB (i.e., not attached via Thunderbolt), I think it's difficult to install the neccessary software to access its SMART attributes (others might know more about this). Plus, personally, I've rarely found SMART information to be very conclusive.
