Random USB 3 External Drive Disconnects

Point taken.

In any case, it certainly doesn't appear to be unique. Maybe that would be a more accurate term?

Thank you, John. I do appreciate your assistance.

I just returned home, and have now tried the SMC reset. I will advise as to the success of that.

In the meantime, I have certainly seen the evidence of your point on the other thread, and I will start that other thread.

I mistook the "I have this problem too" prompt in the Community to indicate a preference for posting in an existing thread with the same subject if it was applicable.

Again,

Thanks

John Galt,

Before I created a new thread on the Time Machine issue, I tried your SMC reset, as I said yesterday. I decided to give it some time and see if it helped, or not.

I waited several hours to see if I got any disconnect messages, and I had NONE. I did also swap the ports, but the same two are still in use, one for the directly connected TM drive, and the other for the USB 3 hub with two other disks attached.

I then ran Time Machine last night, and it DID complete a backup to my external USB 3 drive. Some unusual behavior, but I can live with it. The transfer rate varied between a very fast 150 and very slow .3 /MBs, (monitored with iStatMenu) but at least this time it did NOT cause the entire machine to slow to a crawl. I was able to complete other tasks on the computer, and it did finish! I haven't monitored Time Machine's speed so carefully before, so maybe it runs that way all the time, but it ran for the first time in 8 days.

I turned on Auto backups, to see whether those would work overnight, and when I looked this morning it had indeed completed several incremental backups!

So, your tip on resetting the SMC seems to have done the trick, both for the Time Machine issue, and at least for the time being, for the USB drive disconnects!!

I had previously looked at the SMC and PRAM reset processes, but when I read the "possible reasons to do this" lists, neither mentioned any of the problems I had, so I didn't try them to avoid mucking about in unknown (to me) areas.

Thanks very much for your kind assistance. I appreciate your willingness to help rather than to criticize those who do not know what you do about the machine.

By the way, you mentioned my Amphetamine reference:

I had installed that just during this troubleshooting process, because it had been suggested by someone else that even though one selected the "do not sleep" choices in System Preferences, OSX had in some cases ignored that and some drives would sleep regardless.

So it was a shot in the dark that didn't pan out, and I'm removing it now.

Thanks once more.

I appreciate that fact. I was receiving suggestions from several people, (some of them obviously more interested in actually helping than others), and I didn't know which were which until I had a chance to try them out.

As soon as I had a chance to try the SMC reset, I did. I was also communicating while away from the computer for a substantial part of the weekend. Didn't want folks to think I was ignoring their responses and suggestions just because I couldn't try them until I returned home.

I agree, this sounds like it was indeed a hardware issue, though I am pretty sure that software can definitely affect the operation of the hardware including something that resetting non-volatile memory could fix!

As I posted elsewhere, at this point, my problems BOTH seem to be fixed, primarily by the SMC reset, and possibly assisted by some of the other suggestions, like reloading Sierra, changing cables (again), etc.

In any case, thanks to all who have offered their help. I seem to be all set for now!

Ron

I assumed that was the case (non-uniform speed). The total time seems about right from this point.

It does indeed stop altogether for long periods, but then resumes and continues.

I really appreciate your help. I'm a happy camper now. And so, apparently, is my well-backed-up and much more stable and usable Mac. <g>

Simple (and cheap!) solutions are the best.

Ron