When backing up compressed NTFS Volumes data transfer is extremely slow causing jobs to extend well beyond normal operation.
Data on compressed volumes must first be uncompressed by the OS before being processed by the VSS subsystem. The uncompressed data is then passed through to the AppAssure/Rapid Recovery(RR) Agent and finally sent to the RR Core for compression and deduplication. The process at the source is extremely disk and CPU intensive and can reduce transfer speeds dramatically.
It is recommended to remove compression from the volume. Transfer speeds will return to normal.