[SOLVED] full backup after dirty-bitmap?

[inno-forum]

Will a full backup be performed after a dirty bitmap?

For example
60 GB VM

First Backup take 3 Minutes

INFO: scsi0: dirty-bitmap status: existing bitmap was invalid and has been cleared
INFO: backup is sparse: 15.51 GiB (25%) total zero data
INFO: backup was done incrementally, reused 15.71 GiB (26%)
INFO: Finished Backup of VM 173 (00:03:12)

Second Backup

INFO: scsi0: dirty-bitmap status: existing bitmap was invalid and has been cleared
INFO: backup is sparse: 15.52 GiB (25%) total zero data
INFO: backup was done incrementally, reused 15.67 GiB (26%)
INFO: Finished Backup of VM 173 (00:19:55)

 

[fabian]

the dirty bitmap only has a single purpose - to allow the backup to skip reading unchanged data. even without a bitmap (such as in your case, where the bitmap was cleared for some reason?) the backup will be incremental if a previous matching one exists, but it will have to read the whole disk to find out which parts are changed.

 

[readyspace]

No, a full backup is not automatically performed after a successful incremental backup using a dirty bitmap; subsequent backups can remain incremental if the bitmap stays valid. However, if the dirty bitmap becomes invalid, as seen in the logs where it was cleared, a full backup will be performed.

 

[fabian]

No, a full backup is not automatically performed after a successful incremental backup using a dirty bitmap; subsequent backups can remain incremental if the bitmap stays valid. However, if the dirty bitmap becomes invalid, as seen in the logs where it was cleared, a full backup will be performed.

that is not true. the bitmap only speeds up incremental backups by allowing to skip reads of unchanged chunks, even without a valid bitmap the backup will still be incremental if there is a previous one.