Re: [gentoo-user] [OT] SMR drives (WAS: cryptsetup close and device in use when it is not)

[Frank Steinmetzger <Warp_7@gmx.de>]

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Am Mon, Aug 02, 2021 at 01:38:31PM +0800 schrieb William Kenworthy:

> > Yup. Today I did my (not so) weekly backup and rsynced the repo to the new
> > drive. After that I wanted to compare performance of my old 3 TB drive and
> > the new SMR one by deleting a snapshot from the repo on each drive. But Borg
> > objected on the second deletion, because “the cache was newer”. But that’s
> > okay. I actually like this, as this will prevent me from chaning two repos
> > in parallel which would make them incompatible.
> >
> Keep in  mind that both repos have the same ID - you should also rsync
> the cache and security directories as well as they are now out of sync
> (hence the warning).

That thought crossed my mind recently but I was unsure how to store the
cache. But since the repo is a monolith, it should suffice to rsync
the whole cache directory to the backup drive (or do it as a tar).

The only problem is the temporal sequence:
1. Host A runs borg and gets a current cache.
2. Host B runs borg on the same repo and gets a current cache.
  2a. Host A now has an outdated cache.

Usually, Host B uses Host A via ssh as remote location of the repository.
So I could simply run a borg command on Host A to update the cache somehow.

> Be very careful on how you do this - you are one step away from losing the
> while repo if the cache gets out of sync.  The docs warn against rsyncing
> two repos and then using them at the same time for a good reason.

I won’t use them at the same time. It will always be one direction:
Hosts --[borg]--> Main backup drive --[rsync]--> secondary backup drive

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