Backup retention policy and key backup interval

abudef

Hello,
I have two questions about backups:

What is the relationship between the “Backup retention” values within the schedule and the values in the “Long-term retention of backups” settings?

Is it better to use the “Full backup interval” parameter, or to configure a schedule with the “Force full backup” option? For example, one schedule running once daily Mon–Sat, and another schedule running once daily on Sun with the “Force full backup” option?

versus

I have gone through the documentation at https://docs.xen-orchestra.com/backup, but it is still not entirely clear to me. Thank you.

Pilow

@abudef I've been there, here is my vision on the topic.

in terms of RETENTION of the schedule, if you put 21, not using the FULL BACKUP INTERVAL in the job, you will get : one full and 20 subsequent deltas. on the 22nd point, a delta will be done and the oldest delta (the one just next to the full) will be merged in the full. its like a forever incremental.
Put 7 in FULL BACKUP INTERVAL, and every 7 days (if it runs once every day), it will make a full.

other way to do it : as you told, two schedules, with forced full on sundays.

difference between the two ? you really choose wich day the full occurs.
in the first way, the full is "7 days after the chain begins"

do not mix these two way of configuring, you would have unnecessary fulls in your chain.

in terms of LTR, @florent and @bastien-nollet recommended me this :
if you use LTR (lets says 14Daily, 4Weekly, 2Monthly), keep the SCHEDULE retention to 1
the LTR parameters will keep the retention points as intended
try not to mix with FULL BACKUP INTERVAL

LTR is still early, because i would like the WEEKLY/MONTHLY/ANNUALY to always be fulls or specific merged fulls, this is not the case...
it is still not clear, as you can't choose it, which day is the WEEKLY (sunday ? monday ?) the MONTHLY (1st ? last day of month ?)

trial & error mode activated.

Bastien Nollet

Thanks @Pilow for doing the explanations.

It may be configurable in the future, but for now LTR picks the first backup of the day, week, month and year. Depending on the timezone of your XOA, the first day of the week may either be Monday or Sunday.

There was initially a bug, making LTR pick the last backup of a time period instead of the first, but this has been fixed a couple of months ago.

abudef

Thank you, @pilow @bastien-nollet , for the explanation. It would certainly be worthwhile to expand the documentation to make it clear how these settings relate to each other and how to use them correctly, perhaps with some practical examples.

Pilow

@Bastien-Nollet why doni have weekly or monthly rétention points that are not fulls ?
could not theses rétentions points be merged in fulls when tagged ?

keeping a monthly incremental suppose to also keep previous inc. and based full

Bastien Nollet

@Pilow The backups kept by LTR are just regular backups with a specific tag, which doesn't change how we treat them.

If you want to avoid each of your LTR backup to depend on one another, we recommend to set a full backup interval value to your backup job, which will regularly force a full backup. (even without LTR, having an infinite chain of backups can cause problem in the long term, especially if no healthchecks are made)