[fedora-virt] Virtio-win Windows NIC goes offlineduringbulkcopies

[Greg Scott]

Guys, I'm replaying the sequence of events from last week and I just
realized - the default Realtech driver also went offline before I put in
the VirtIO NIC driver.  Here's the sequence:

1 - Start an ntbackup of everything from the physical 2003 server to the
2008R2 virtual machine on a RHEL libvirt host, about 230 GB.  The 2008R2
server was using the default Realtech NIC driver.  
2 - The 2003 ntbackup projected around 24 hours to complete the backup
using a 1 gb switch. This felt excessive, but still doable, so I let it
run.  
3 - About 8 hours in - around 4AM - at roughly 100GB, the 2008R2 virtual
machine went offline. 
4 - Without any serious troubleshooting, I shutdown the 2008R2 VM,
removed the Realtech NIC, and added two Virtio NICs.  
5 - Starting up my ntbackup again, this time ntbackup projected about 8
hours to completion.
6 - But the VirtIO driver on the 2008R2 system continued going offline
at random times.  It took several occurrences of this before I realized
that disabling and re-enabling the 2008R2 NIC temporarily cleared the
problem - but I would have to restart ntbackup every time. 

When that first Realtech driver went offline, I had not characterized
the problem yet, and realizing I did not want to use the Realtech driver
anyway, I just took it out and put in 2 virtual NICs, both using the
VirtIO driver instead.  That virtual machine will connect to 2 separate
networks - that's why the 2 NICs.  

So that Realtech problem could have been something else, but looking
back, I don't think so. I wonder if the VirtIO and hardware emulator
drivers share some common code?  Or maybe there's a flow control issue
effecting them both?

- Greg Scott