deduplication

Hi ALL,

we are working on using deduplication technology in our environment but want to have below things clear:Just the basic idea?

1. Before NBU 7.x,How do we do deduplication? we use symantec netbackup pure disk?
2. Symantec NetBackup PureDisk is a product that provides a complete backup and deduplication environment. It can be used as a stand-alone (PureDisk writes data to the storage pools) or as a back-end for NetBackup. How it is use as standalone and as backend?
3. now in 7.1 we have MSDP.This is also using Pure disk?
4. What is this MSDP?And this PDDO?