You could see data transfer on switch port for example... There is no straight way of doing it. However, time really depends on many variables and you can't give simple estimate just like that. The easiest way to guess would be to say same amount of time required for backup.

Legato provides a utility - Blaster but that checks the data transfer rate on the network. Backup time would also need the writing capabilities of the backup device. Also, blaster is for Unix environment.

Blaster does exist for Windows environment (however it was made for NT so I can't say how does it perform on modern Windows boxes). Blaster tests can't be used to interpret real network state - just to identify potential network bottlenecks.

First of all, you need to know how long was this backup. Most of times, people would say that recover takes 1.5 times the backup time in average, but it depends on a lot of things (for example, multiplexing speed up backups but increases restore times).

You can monitor restore progress via NMC (Monitoring -> Sessions -> Recocver Sessions), it will show you some statistics, including "% complete"... But it's up to you believe in this info

Would Multiplexing cause significant increases in restore times, for instance, days. I started an Exchange database storage last week and it is still running. But takes only about 90 minutes to back up 130 GB. Haven't found out why yet. Got a ticket in with Legato but so far no resolution. My normal data and SQL restores are very quick, only affecting Exchange databases.

I checked out the recover session in NMC but it shows nothing even though I am running an Exchange DB restore as we speak.

I believe multiplexing slows down the recovery and the same is true for parallelism if kept high.

Well, a 90 minutes backup won't take one week to restore. I believe that the best you have to do is go on with this ticket and pray for support to give you a quick solution, and they problably we'll give you the answer for your problem. When it's finished, tell us which was the solution.