SRM Failback use long long time

I am using VSphere replication to replicate a VM which has 100GB data.

In SRM, to execute the recovery plan just used around 4 min, the VM running in DR site without any problem.

However, when I would like to failback this VM
1. I click reprotect....used around 6 hours to initial full Sync from site B to site A
2. Then use 5 min to recovery the VM from site B back to site A
3. Finally use 6 hours to initial full sync from site A to site B

So, Total I used around 12 hours to failback the VM to it original site.

I would ask it is normal to take much time for initial sync?  If use storage array replication, will the initial sync take little time?

I still has some protected VM which with 800GB data disk and I think I need 1 week to failback the VM.