How Does Backup Retention Work With Delta Backups and Full Backup Interval
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I think this is best explained with an example, I know that if you have Delta backups setup with a retention of say 7 and nightly backups, then you get a full backup, 6 deltas, and then the oldest delta coalesces into the full backup.
But, let me propose this scenario:
-Delta Backup set to run nightly, retention of 14
-Full backup interval setup for 7So when the retention period of 14 is met, there are 2 full backups (i.e. 2 backup chains), what does XOA do with the older full backup, does it delete it since it's outside the retention? In that case does it delete the whole 1st chain?
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@planedrop No, as you have a 14 day retention we will always keep a 14 days backup, in fact the 7 day full backup interval is not really link to the backup job you could have a delta of 14 days, the 7 day full backup is here to protect from delta chain corruption.
So what will happen is that XO will always keep the full that started the delta chain, and it will merge the older delta (day 13) with the main full so the delta chain will keep 14 days retention, the full backup interval is not taken into account in this as it is not part of the delta chain.
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@darkbeldin Oh alright, I think I'm understanding this now.
Just to be clear, the new full backup doesn't become part of the chain, it's basically an entirely separate backup?
Essentially it'd almost be like running 2 jobs separately, one as a 7 day full backup and the other as a 14 day delta, but this just puts them all into a single job.
Thanks a bunch!!
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@planedrop No not completely, the full are part of the delta chain, they are treated as delta but instead of a delta you have a full as part of the chain and the chain is secured by this full has a "recovery point" if the chain is corrupted so if you lose part of the chain you could recover more.
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@darkbeldin Ohhhhh ok.
So one last thing, once a periodic full hits the retention period, it then gets coalesced into the original full right? (or does it just delete it?)
Pinging @olivierlambert on this too because my understanding was that the periodic full became the new backup chain, and that seems to be what the documentation says as well:
"For example, with a value of 2, the first two backups will be a full and a delta, and the third will start a new chain with a full backup."
https://xen-orchestra.com/docs/delta_backups.html#introduction
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It's better to ping @julien-f instead
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@olivierlambert Sounds good, thank you!
