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

Benny Kjær Nielsen mailinglist at freron.com
Sat Dec 16 06:51:04 EST 2017

On 11 Dec 2017, at 22:38, Charlie Garrison wrote:

> On 12 Dec 2017, at 1:42, Benny Kjær Nielsen wrote:
>> I was going to suggest leaving out the index 
>> (the `Database.noindex` folder) since that doesn't behave well with 
>> Time Machine.
> Could you please expand on that? What is the issue with backing up the 
> index? Is it something specific to Time Machine or backups in general?

It's a combination of a MailMate issue and a Time machine issue.

1. MailMate separates files by headers. This means that a file for, 
e.g., `from` is changed whenever a new message arrives triggering it to 
be backed up again. And some of these files can be huge for large 
message stores.

Even if I improved the above it wouldn't solve the second problem:

2. MailMate is very careful about the database not getting corrupted 
even if MailMate or the machine crashes at any given time while it is 
saving data. This includes rolling back to the most recent complete 
state. Unfortunately, MailMate cannot control the order that the files 
are backed up which means that not all files backed up are necessarily 
from the same “revision” of the database. Therefore restoring from a 
backup can very easily resulted in a corrupted database.

I haven't found a good solution to the second problem.

> More importantly, is it an issue that snapshots will solve?


> (I’m doing a custom backup of just MailMate, specifically so I 
> don’t lose the index; rebuilding it is NOT fun. It seems to work 
> just fine but maybe I’m missing some hidden problems.)

A robust backup solution for MailMate should ensure that MailMate is not 
running while doing the backup.

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