VirtIo errors inside VM with UFS-in-zvol

Peter Grehan grehan at
Mon Aug 25 18:50:29 UTC 2014

Hi Marat,

>>    vtbd0: hard error cmd=write 290-305
> I would like to report the same problem. I'm using  10.0-RELEASE-p7 as a
> host, and 9.3-RELEASE as a guest. VM is created using vmrc script, it
> installed fine. But on attempt to create additional fs inside the vm,
> newfs just silently fails without writing anything to disk.  file -s on
> a filesystem reports just 'data', instead of the usual "Unix Fast File
> system"

  This issue is caused by the FreeBSD GEOM code tasting the zvol, 
parsing partition/slice tables, and marking sections read-only.

  There is a fix for this by mav@ in r264145 in CURRENT, and MFC'd to 
10-STABLE in r265678 (May 8). The fix will be in 10.1.

  The zfs man page lists the new zvol property and sysctls that can be 
used to prevent GEOM testing.



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