Real Device with BHyve

[Andrea Brancatelli]

Hello everybody.

I'm doing some experiments with bhyve on 10.0-RC3 and I got stuck at a
certain point.

I was trying to have a VM use a direct device (/dev/da2) instead of a disk
image. I was trying it in order to understand if there was any real
performance difference between using a raw drive or an image-disk on the
same drive.

Well, the machine starts ok but when the "child" FreeBSD starts
installation something strange happens. When I get to the partitioning
screen I can see the device avaiable as /dev/vtdb0 with the correct size
and such. I choose autopartitioning, the installer writes the partition
table but when it start to write /dev/vtdb0p2 a very cryptic error appears
about being unable to write - sorry, did not write it down.

The installer then stops.

If I do a fdisk /dev/vtdb0 in the VM I can see the GPT partition being
there. If I do a fdisk /dev/da2 on the host machine, I can see the GPT
partition as well, but the VM just doesn't want to write on it.

I even tried changing kern.geom.debugflags=16 as I thought the host machine
could be locking somehow the drive, but that didn't seem to make any
difference. I know it was a lame check but I was out of ideas.

So I just wanted to understand if such a scenario is supposed to be
supported....

What I was thinking of, for example, was of having an external iSCSI device
connected on the hostmachine mapped as a virtual disk for a specific VM, in
order to speed the VM disk performances.


Just another quick question... I have seen some improvements by having the
VM's virtual disk on ZFS against UFS. Is it just me or is there any real
improvement by using ZFS?

Thanks a lot.


-- 




*Andrea BrancatelliSchema 31 S.r.l. - Socio UnicoResponsabile ITROMA -
FIRENZE - PALERMO ITALYTel: +39. 06.98.358.472*

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