I’m having second thoughts about migrating towards borg backup
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The main issue is how to handle β€œ3rd strand” backup. I use a removable HDD that I sync with my main backups monthly and lives outside my house the rest of time
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Borg strongly discourages syncing their backup repos using file-level tools like rsync.
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Replying to @jmtd
AFAICT (we borg quite a bit) this is because they make no guarantees as to how much of the repo they touch during a backup, and rsyncing during such an event might result in a broken 3rd strand. So long as you're careful to not hit that, you should be fine.

Sep 28, 2020 Β· 7:58 AM UTC

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Replying to @dsilverstone
Yeah, I’ll arrange all the jobs to be mutex (via systemd units). It still doesn’t give me the warm fuzzies. There’s some potential issue about a client (eg a restore operation) being unhappy if you ask it to talk to two repos with the same uuid
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I've never had to use our 3rd-level in anger, but my plan is to restore (rsync) to the 2nd-level and restore (borg) from there if ever needed.