[MlMt] High Sierra, APFS, Time Machine, and MailMate...
Steven M. Bellovin
smb at cs.columbia.edu
Sun Dec 10 21:14:21 EST 2017
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
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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