Deduplication for Remote backups

Client side de-dupe and accelerator work well for remote offices but if your storage is local to the remote site then MSDP on both sites is the way to go and just use a SLP to control the data flow - so backup is MSDP storage on remote site and Duplication to MSDP at local site

Should work OK - just makes me wonder what else you do at the local site?

If you have 4.5 TB at Site A and 5 TB at Site B i get the feeling that you probably do backups at site B too - so do make sure you actually have enough free space at Site B to duplicate the backups from Site A to it without filling it up - also set your retention periods carefully when doing this

Generally if you do backups at both sites and want to duplicate one site to the other you would want a much larger MSDP pool at site B

Hope this helps