Hyper V Instant recovery

[manfri]

From my testing it's required to have as much as disk as the vm to be launched, because it preallocate the vhdx.

I've understood correctly?

And, maybe with some refs trick (copy on write, sparse file system...), before commiting the restore, it's possible that this is not really necessary?

[vClintWyckoff]

Hey Marco-
When we perform an Instant VM Recovery on Hyper-V we create a "dummy" VM with the exact same settings as the Production VM had at the time of the chosen restore point, a protective snapshot is taken and then via Veeam data mover services the disks from your backup repository are mounted. At this point, the backup is running from the repository however to the HV environment things appear to be running from the local CSV (for instance). If the production VM was dynamically expanding and only using 24GB of 60GB that's all the HV host thinks is using. When you migrate the VM from the repository to the production Hyper-V host, if the VM was dynamically expanding those settings are maintained.

Is the production VM a fixd VHD(x) or Dynamically Expanding?

[manfri]

Dynamically Expanding
In my test the VHDX is preallocated of the dimension of the data in use (not the maximum size of VHDX) but if i have a 4TB VM is not someting to be overlooked.

In fact i'm hoping that it's something i did wrong

If this is not configurable can be a mess
And i wonder if there is real need to preallocate before "committing" the recovery.

[DGrinev]

Hi Marco,

In case of dynamic disks, pre-allocated space will be equal to the size of data in use. Thanks!