freebsd stable - Feb 2014 - recovering from or increasing timeouts on virtio block device

I run several FreeBSD virtual machines in a Linux KVM environment with a SAN.
The VMs use virtio block storage, and the KVM hosts map the virtual volumes to
targets on the SAN. Occasionally, failover or other maintenance events on the
SAN cause it to be unavailable for 30+ seconds. When this happens, the FreeBSD
VMs have hard failures on the vtbd* devices, and thereafter any attempted reads
or writes return immediately with an error (even after the SAN is responsive
again). The only way to recover a VM once that happens is to hard boot it.

Is there any way to adjust the timeouts or enable some kind of retry for the
virtio block devices? It would be nice to be able to recover gracefully after a
SAN event without needing to reboot the VMs.

Thanks!

John Nielsen

Wiadomo?? napisana przez John Nielsen w dniu 17 lut 2014, o godz.
21:21:
> I run several FreeBSD virtual machines in a Linux KVM environment with a
SAN. The VMs use virtio block storage, and the KVM hosts map the virtual volumes
to targets on the SAN. Occasionally, failover or other maintenance events on the
SAN cause it to be unavailable for 30+ seconds. When this happens, the FreeBSD
VMs have hard failures on the vtbd* devices, and thereafter any attempted reads
or writes return immediately with an error (even after the SAN is responsive
again). The only way to recover a VM once that happens is to hard boot it.
> 
> Is there any way to adjust the timeouts or enable some kind of retry for
the virtio block devices? It would be nice to be able to recover gracefully
after a SAN event without needing to reboot the VMs.
Use gmountver(8) perhaps?

-- 
If you cut off my head, what would I say?  Me and my head, or me and my body?