Quick Migration job slow vs restore entire VM to Nutanix AHV

[arngrimurm]

Case #07680671
The title says it all.
Backing up one VM takes 1 minute, restoring the same complete VM is the same as backing it up or 1 minute.
But doing Instant Recovery and then do "Migrate to production/Quick Migration" takes 25 minutes.
Is that "by design" or what could be wrong?

[Kochkin]

Migration is done by Nutanix software (they read data from NFS datastore and write to own datastore)

Nutanix side does not have information about sparse areas. So if your disk is mostly sparse, entire VM restore might be faster. IR migration will read and write all the zero blocks, so it is slower indeed.