Compression question with Win client & server

I’m evaluating this for home use.

I set up a test server, on a Win 10 laptop (fresh install), laptop has a 600g drive

I installed the client on my main computer, and configured it to backup one of my drives, files (not image)

The drive being backed up has about 830 gig of data on it.

Network is a 1 Gbit lan, but the laptop has a 100Mbit NIC.

Backup took 22 hours.

Log says:
Transferred 775.795 GB - Average speed: 81.7317 MBit/s
(Before compression: 10.715 GB ratio: 0.0138116)
Time taken for backing up client Son-of-Godzilla: 22h 51m 41s
Backup failed

No reason why it failed.
Laptop still has about 400g of free space.

So, a couple of questions:

  1. why did it fail, where can I find out why?
  2. If it transferred 775g of data, would the failure have been running out of space?
  3. From reading the documentation, it seems that urBackup doesn’t do compression on it’s own, but relies on the underlying OS/filesystem to do the compression. Is this correct?

Thanks in advance