I was doing some tests with my two instance's of SQL Server 2008 R2 and 10 Mbps limited LAN. I setup synchronous database mirroring. Database log file is 25000 MB and 99% free before the test.
I started to move some records and rebuild every index in database, that took 2 hours and 7 minutes. For the last hour in that test the network utilization was 99% used, before that the usage was up and down. Immediately after test ended (2 hours and 7 minutes) the network utilization went to 0%.
After these actions database log file is 23% free which means that this test generated 19 GB of log records.
How can 19 GB of log records be transferred to mirror instance if my network has 10 Mbps? 10 Mbps has 1.20 MB/s which means it would take than 4 hours to transfer all that data?