[MlMt] High Sierra, APFS, Time Machine, and MailMate...

[Paul Sture]

On 11 Dec 2017, at 3:14, Steven M. Bellovin wrote:

> Seems like an improbable subject line--but is anyone else who uses 
> MailMate on High Sierra/APFS suddenly having serious Time Machine 
> performance issues? I am, on two different laptops. An iMac, which has 
> a hard drive and hence HFS+, is not having any trouble.
>
> The overall symptom is that backups take *many hours*, with sudden, 
> inexplicable stalls. I say "inexplicable" because Activity Monitor 
> shows essentially no CPU, network, or disk activity -- but the backup 
> just *stops*. I normally don't run MailMate on one of the laptops; its 
> backups complete in a rational amount of time. When I do, it sees the 
> same stalls. In fact, I'm running MailMate on it right now so that I 
> can see what happens on my primary laptop when I exit MailMate. Sure 
> enough, that machine is now behaving.
>
> My suspicion is that the problem has to do with very large directories 
> on APFS file systems, but I don't know that for sure. I have some very 
> large mailboxes, though, and these are of course active when MailMate 
> is running.  And of course, that doesn't explain why I don't see any 
> system activity.
>
> Is anyone else seeing this? Does anyone have any work-arounds, other 
> than "don't have such large mailboxes" or "don't run APFS"? I do have 
> a new laptop on order; I'm seriously tempted to reformat it as HFS+ 
> before I start using it.
>

I saw something similar last week when I wiped my TM disk and started 
afresh. TM got to 120GB out of 750GB and then showed little progress for 
several hours.

I resolved it by quitting various apps.  I cannot recall which one I 
quit that got TM working again, but I have quite a few that clock up CPU 
and I/O even when not in focus.

The following StackExchange article may shed some light.

https://apple.stackexchange.com/questions/212537/time-machine-ridiculously-slow-after-el-capitan-upgrade

Scroll down to the first answer for details.