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

[Roger Bohn]

I have had this situation for many YEARS, long before I got MailMate.
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*.

The problem is worse, the more Time Machine needs to back up. And for 
reasons I have never figured out, even a routine backup on TM (of a few 
hours of material) can have 5GB of files to go through. As a result, I 
can get into a situation where TM is completely unable to get up to 
date.

So I don’t know a solution, but don’t be too sure that it is really 
due to MM. If anyone finds a solution, please drop me a line!
   One thing that helps is to switch from WiFi to a hard ethernet 
connection. For some reason, TM is considerably faster that way.

  Roger Bohn, UC San Diego
Rbohn at ucsd.edu

On 10 Dec 2017, at 18:14, 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.
>
>
>         --Steve Bellovin, https://www.cs.columbia.edu/~smb
>
>
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