Question: Delta backup retention vs. full backup interval


  • It is not fully clear to me if "full backup interval" is really needed (for preventing corrupted backups over the time) with delta backups wich are supposed to be "continous" and which are merging in new deltas automatically.

    So is it really suggested to set a full backup interval with continous delta backups ?

    And what means that in practice for disk usage ? If we have for example an retention of 3 and a full backup intervall of 5. Will it mean :
    1st backup : Full
    2nd backup : Delta
    3rd backup : Delta
    4th backup : Delta (now the 2nd delta gets new "full")
    5th backup : Full (now 3rd delta becomes another "full" and we have 2 fulls ?)

    I am confused. Maybe you could help me understand this mechanism better.

  • XCP-ng Team

    Ping @julien-f to explain and/or update the doc to make it more clear.

  • XO Team

    Hi,

    Did you read the documentation? 🙂


  • @Vinylrider your understanding is correct, delta retention is just how many deltas to keep before merging the oldest delta with the full. Full backup interval is the time between each new full back up for use in case of corrupted back up.

    To answer your question, yes it is recommended to have more than 1 full back up to fall back to in the event of corruption espcially of delta backups since delta backups rely on previous deltas meaning if one of your delta is corrupted, you'll loose all data from that point onward until another full backup is made, or worse your full backup could be corrupted (more likely because of the file size) then you loose the whole chain. And if your corrupted delta is merged with the full, you'll probably have a corrupted chain aswell.

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