The backup software itself needs to be 64-bit native to efficiently manage the large memory blocks required for compression and encryption processes.
As your virtual host grows to 128GB, 256GB, or even 1TB of RAM, a 64-bit backup engine can scale its memory usage to handle the increased metadata load. Best Practices for Implementation virtual backup 64 bit
VMs often have massive virtual disks that require high-speed deduplication. The backup software itself needs to be 64-bit