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

David Ledger mailmate at ivdcs.co.uk
Mon Dec 11 05:31:02 EST 2017

On 11 Dec 2017, at 2:14, 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.

Having read the other replies I would question Activity Monitor. AM is 
an application built on top of the real data recording and it wouldn’t 
surprise me in the least if Apple filter out any sort of activity they 
think you shouldn’t be concerned with. Try using ‘top’ in a 
terminal window. Unless Apple have doctored a long standing utility that 
will tell you what is really going on. Running ‘top’ without 
arguments, the header gives you:

	Load Average (which is the number of processes waiting for the CPU 
averaged over 1, 5, and 15 minutes - an indication of overall load, more 
useful for servers,
	CPU usage (and idle %age),
	Memory usage,
	Network traffic, and
	Disk I/O

It updates every second (by default). The report below the header is at 
a per-process level. It’s surprising how busy the system really is.

Hitting the ‘q’ key stops it. ’man top’ will tell you how to 
control the rest of the o/p.

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