[Borgbackup] Baffling behavior on low cpu system with borg backup

[Thomas Waldmann]

>>> To be clear, every single time I have blown away the cache and retried the
>>> backup operation, borg has synchronized and completed the backup
>>> successfully.
>>
>> Can you check how big the "chunks" cache is after that?
> I'm not sure how I would do that.

# find out repo's ID:
repo-server$ grep ^id repo/config

# check size of chunks cache:
raspi$ ls -l ~/.cache/borg/<id>/chunks
main-server$  ls -l ~/.cache/borg/<id>/chunks

For the latter 2, you need to be logged in as the user running the borg 
backups (root?).

> When I do that test this weekend I'll first try simplifying the required
> steps and see if I get the same sort of hang; I'll try backing up a single
> file, then muck around with the server side so it has to resync

You can trigger a resync by modifying 1 digit of the manifest in the 
cache's config - borg will then think the cache is out of sync:

[cache]
...
manifest = 43867a6f631e3ea4e7520e62904ac26615566b2a3c7a0b42656900f0e2074032
...

> I'll also run a full backup from a clean cache using time so you can see how
> long it takes when it works, and record the memory use of borg (maybe using
> a script to write ps output in 1 min intervals?) on both the Rpi and the
> server when I have them doing tasks.

On the client (raspi), you could use:

/usr/bin/time borg ...

The memory usage of the borg repo server is maybe not that interesting.

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