[Users] EL5 support for VirtIO SCSI?

Thu Nov 14 07:39:33 UTC 2013

Adding Stefan with the correct email this time.

----- Original Message -----
> Hi Paul,
> 
> First of all, thanks for the detailed answer, it really helps.
> See comments inline.
> 
> ----- Original Message -----
> > Hello Itamar.
> > The specific use case is a particular propriety filesystem that needs to
> > see
> > a scsi device. It will do scsi inquiry conmmands to verify suitability.
> > In talking to the devs - of the filesystem - there is no way around it. I'd
> > previously tried virtio-block - resulting in the /dev/vd* device - and the
> > filesystem would not work.
> > 
> > From doing a bit of web searching it appears the kvm/qemu supports (or did
> > support) an emulated LSI scsi controller. My understanding is that the
> > various virtualization platforms will emulate a well supported device (by
> > the guest OSes) so that drivers are not an issue. For example this should
> > allow a VM on Vmware vsphere/vcenter to be exported to Ovirt and have it
> > boot up. The potential for further optimising the guest is there by
> > installing ovirt/qemu/kvm guest utils that then allow the guest OS to
> > understand the virtio nic and scsi devices. The guest could then be shut
> > down, the nic and scsi controller changed and the guest booted up again.
> > You can do the same thing in the Vmware world by installing their guest
> > tools, shutting down the guest VM, then reconfiguring it with a vmxnet3 nic
> > and pvscsi scsi adapter, then booting up again.
> > It does seem somewhat inconsistent in Ovirt that we allow a choice of Intel
> > e1000 or virtio nics, but do not offer any choice with the scsi adapter.
> 
> virtio-scsi support was just recently added to oVirt to allow for scsi
> passthrough and improved performance over virtio-blk.
> I believe the emulated scsi device in qemu never matured enough but possibly
> Stefan (cc'd) can correct me here.
> For simplicity sake we kept choosing the controller type out but there is
> nothing in the design preventing one from adding it.  This is however the
> first time I've actually heard any requests for it.
> Note that using hooks you can still enable any functionality that qemu-kvm
> supports but is not exposed in the GUI.  It's not the most elegant way, but
> it works.
> 
> > Again, in Vmware land you can choose to have a scsi disk, but you choose
> > which controller type it is attached to. In the current Ovirt 3.3.0 release
> > you just chose a virtio-scsi disk, rather than there being a separation of
> > the scsi disk and scsi controller.
> > The messy situation with importing VMs from other platforms could be eased
> > by
> > allowing an emulated scsi controller as well as the preferred virtio
> > controller.
> > As mentioned previously, the support for this seems to be present in
> > kvm/qemu. I wonder if there was a specific design decision (ie: some
> > particular reason) to not support the approach I've just described? I can
> > understand that in some cases simplicity is something to aim for though.
> > I think this would make migration away from the dominant market leader -
> > Vmware - easier and is something that would make ovirt/RHEV that more
> > compelling.
> > 
> > Getting back to my original query - 'open-vm-tools' support the vmware
> > paravirtual scsi adapter and I am able to install these on EL5 and then see
> > that adapter. It would be great if there was a similar initiative for the
> > various virtio devices where you could install a packge/kmod and then allow
> > some of the older OSes (of which there are still lots of VMs around for
> > various reasons). There are obviously drivers for the various Windows
> > flavours that take this approach. I'm surprised that for Linux it is just a
> > case of 'if it's in the kernel you are running then it is supported'.
> > 
> > I'm really pleased with the progress the ovirt has been making. I'm like to
> > see it continue to knock down the various reasons out there as to why
> > people
> > with Vmware vcenter shops can't migrate over to it.
> > 
> > Cheers,
> > Paul
> > 
> > 
> > On Wednesday, 13 November 2013 8:57 PM, Itamar Heim <iheim at redhat.com>
> > wrote:
> > On 11/13/2013 03:58 AM, Paul Jansen wrote:
> > > Hi Rene.
> > > I specifically need the scsi support (virtio-scsi).
> > > I do know about the virtio-block support, which results in /dev/vd*
> > > devices as you say.
> > > From what I read even EL6 earlier than 6.3 does not support virtio-scsi
> > > 
> > > Alternatively, does oVirt support an emulated scsi adapter of a
> > > different type that would allow me to see scsi disks?
> > 
> > may i ask why do you need the virtual disks to specifically be scsi?
> > 
> > > 
> > > Regards,
> > > Paul
> > > 
> > > 
> > > On Wednesday, 13 November 2013 7:23 PM, René Koch (ovido)
> > > < r.koch at ovido.at > wrote:
> > > On Wed, 2013-11-13 at 09:41 +0100, Sander Grendelman wrote:
> > > > According to https://access.redhat.com/site/solutions/20511
> > > < https://access.redhat.com/site/solutions/20511 >virtio
> > > > work on > rhel5.3.
> > > > 
> > > > You have to edit /etc/modprobe.conf and generate a new initrd.
> > > 
> > > 
> > > If you're installing the OS on a VirtIO disk this is done automatically
> > > by anaconda. I just installed RHEL 5 on oVirt 3.3 with VirtIO disk and
> > > everything worked out of the box.
> > > 
> > > 
> > > > 
> > > > On Wed, Nov 13, 2013 at 9:32 AM, Sven Kieske < S.Kieske at mittwald.de
> > > <mailto: S.Kieske at mittwald.de >> wrote:
> > > > > Hi,
> > > > > 
> > > > > afaik the rhel 5 kernel series just has not the necessary drivers for
> > > > > all virtio stuff, so it's not supported and does not work, unless
> > > > > you want to patch your own kernel.
> > > > > 
> > > > > Am 13.11.2013 06:44, schrieb Paul Jansen:
> > > > >> I have just set up an Ovirt 3.3.0 install and have done a test
> > > install of Centos 6.4 in a VM. The VM was configured with an IDE drive
> > > and a virtio-scsi drive. The Centos 6.4 install sees both drives OK.
> > > > >> I'm wanting to do some testing on a product that is based on EL5,
> > > but I'm finding that it cannot see the virtio-scsi drive. It does show
> > > up in the output of 'lspci', but I don't see a corresponding 'sd' device.
> > > > >> 
> > > 
> > > 
> > > There's no /dev/sd* device - the devices are named /dev/vd*...
> > > 
> > > 
> > > > >> I've just tried installing Centos 5.10 and the support is not there.
> > > 
> > > 
> > > Didn't test CentOS but RHEL 5 is working fine.
> > > 
> > > 
> > > Regards,
> > > René
> > > 
> > > 
> > > 
> > > > >> 
> > > > >> Does anyone know of any tricks to allow EL5 to see the virtio-scsi
> > > device?
> > > > > 
> > > > > 
> > > > > --
> > > > > Mit freundlichen Grüßen / Regards
> > > > > 
> > > > > Sven Kieske
> > > > > 
> > > > > Systemadministrator
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