why this? "INFO: scsi0: dirty-bitmap status: disabled (VM not running)"

XoCluTch

Member
Jul 29, 2018
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Why are backups not not incremental if the VM is offline?

Why does it matter if the VM is running or not to perform an incremental backup?


Thanks
 

tom

Proxmox Staff Member
Staff member
Aug 29, 2006
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Why are backups not not incremental if the VM is offline?

Why does it matter if the VM is running or not to perform an incremental backup?


Thanks

Backups are always incremental, why do you think they are not? You have to read the full disk but you save just the change to the backup.

As long as the VM is running, by using qemu dirty-bitmaps only the dirty-bitmap have to be in the backup.
 

XoCluTch

Member
Jul 29, 2018
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Well if the VM is running, it finds and runs a dirty bitmap and only transfers the "delta".

What's happening with offline VMs. Is that it says because it's offline it's not using a bitmap and then transfering the full disk.


It appears of the server the backup is still incremental. But it's taking a LONG time to process/transfer offline VMs instead of less then 1-2 seconds for other VMS.
 

tom

Proxmox Staff Member
Staff member
Aug 29, 2006
15,496
889
163
Well if the VM is running, it finds and runs a dirty bitmap and only transfers the "delta".

What's happening with offline VMs. Is that it says because it's offline it's not using a bitmap and then transfering the full disk.

No, just analyse the backup log and the network traffic. Only changes are written to the backup store.

And yes, dirty-bitmap backups are ultrafast. In almost all server setups VM are running 24/7, so this is the normal use case for most.
 

XoCluTch

Member
Jul 29, 2018
24
3
8
38
No, just analyse the backup log and the network traffic. Only changes are written to the backup store.

And yes, dirty-bitmap backups are ultrafast. In almost all server setups VM are running 24/7, so this is the normal use case for most.


Well that's my question. Why is the dirty-bitmap not being used for an offline VM.

I thought it might be a bug.
 

XoCluTch

Member
Jul 29, 2018
24
3
8
38
is it possible to maybe have an option to help with backups related to offline VMs like...

Skip offline VMs if they have not been run since last backup?


Thanks for the info guys.
 
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