Time Machine unable to complete backup

[AMSOS]

Recently Time Machine takes forever to back to my 1TB external. There's still about 320GB of space, so I am not sure why this is happening.

I went ahead and deleted old backups that I can see in the TM folders. These are from ten years ago and not needed anymore. Even now, however, it seem to be taking too much time to backup.

The last backup said it needs 5 hours or more to complete, so I cancelled it when it was at 16 percent.

Do I need a new disk (this one seems fine but it is 8 years old and lightly used)?

Is there some TM setting that I need to know about to resolve this?

Thanks!

 

[maflynn]

Did you check the SMART status of the drive?

The beauty of Time Machine is the lack of settings, so if backups are taking a significant amount of time, then there's only a few reasons why

 

[Bigwaff]

I went ahead and deleted old backups that I can see in the TM folders. These are from ten years ago and not needed anymore. Even now, however, it seem to be taking too much time to backup.

If you had 10 yr old backups on TM drive then this really old TM drive formatted HFS+. APFS TM drives have only been around for about 5 yrs or so. What make/model/spec of ext drive used for TM? What version macOS using and what are TM settings? Backing up other external drives to TM? Are you using TM drive for data and for backups? TM disk partitioned?