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

Charlie Garrison charlie-lists at garrison.com.au
Sun Dec 10 21:31:43 EST 2017

On 11 Dec 2017, at 13:14, 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.

Time Machine is working normally for me.

You didn’t see what your Time Machine destination is. That would be my 
first suspect.

> 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.

Note, TimeMachine takes a snapshot when backing up APFS volumes, so 
there “shouldn’t” be any difference with MailMate running or not. 
I suspect that’s really a symptom of what the real problem is.

> 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.

Due to the way APFS works, I’d be surprised if that’s the issue.

> 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.

If that new laptop has an SSD, then APFS is your only choice.



     Charlie Garrison                   <charlie at garrison.com.au>
     Garrison Computer Services      <http://www.garrison.com.au>
     PO Box 380
     Tumbarumba NSW 2653  Australia

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