And now for a walk on the wild side…
You can map various Network shares or Local VMDKs to the DataRecovery Appliance.
Assuming that you are hosting you’re DR appliance on ESX1
You could in Theory, create a new VirtualMachine running OpenFiler on ESX2 and ESX3, and map you’re DR Appliance onto these shares.
When you create backup jobs, you can select the destination to store you’re backup files, VM’s from ESX1 are stored on ESX2 local disk, ESX2 VMs on ESX3 local disk etc…
This is just design ranting, and would complicate matters and network performances.
Alternatively, you could use vCenter Orchestrator and make a backup workflow that makes backups from ESX1 > ESX2, ESX2 > ESX3, ESX3 > ESX1. I have done such a design 3 years ago with Orchestrator (it was Dunes VS-O then)