[ovirt-users] vhostmd vdsm-hook

[Arsène Gschwind]

I've never tried with 2 disks but I will assume that the next free 
available disk will be used by the vdsm hook and the vm-dump-metrics cmd 
will check the kind of disk.
Let me know if you give a try....

thanks,
Arsène

On 04/19/2016 02:43 PM, Simon Barrett wrote:
>
> Thanks again but how does that work when a VM is configured to have 
> more than one disk?
>
> If I have a VM with a /dev/vda disk and a /dev/vdb disk, when I turn 
> the vhostmd hook on the vm metric device gets created  as /dev/vdb and 
> the original /dev/vdb disk gets bumped to /dev/vdc.
>
> Is that expected behavior? Will that not cause problems?
>
> Thanks,
>
> Simon
>
> *From:*Arsène Gschwind [mailto:arsene.gschwind at unibas.ch]
> *Sent:* Tuesday, 19 April, 2016 13:06
> *To:* Simon Barrett <Simon.Barrett at tradingscreen.com>; users at ovirt.org
> *Subject:* Re: [ovirt-users] vhostmd vdsm-hook
>
> The metric information are available on this additional disk /dev/vdb. 
> You may install the package vm-dump-metrics and use the command 
> vm-dump-metrics which will display all metrics in an xml format.
>
> Arsène
>
> On 04/19/2016 10:48 AM, Simon Barrett wrote:
>
>     Thanks Arsène,
>
>     I have vhostmd running on the ovirt node and have set the
>     sap_agent to true on the VM configuration. I also stopped and
>     started the VM to ensure that the config change took effect.
>
>     On the oVirt node I see the vhostmd running and see the following
>     entry in the qemu-kvm output:
>
>     drive
>     file=/dev/shm/vhostmd0,if=none,id=drive-virtio-disk701,readonly=on,format=raw
>     -device
>     virtio-blk-pci,scsi=off,bus=pci.0,addr=0x8,drive=drive-virtio-disk701,id=virtio-disk701
>
>     The part I wasn’t quite understanding was how this presented
>     itself on the VM but I now see a new disk device “/dev/vdb”. If I
>     cat the contents of /dev/vdb I now see the information that is
>     provided from the ovirt node, which is great news and very useful.
>
>     Thanks for your help.
>
>     Simon
>
>     *From:*users-bounces at ovirt.org <mailto:users-bounces at ovirt.org>
>     [mailto:users-bounces at ovirt.org] *On Behalf Of *Arsène Gschwind
>     *Sent:* Monday, 18 April, 2016 16:03
>     *To:* users at ovirt.org <mailto:users at ovirt.org>
>     *Subject:* Re: [ovirt-users] vhostmd vdsm-hook
>
>     Hi Simon,
>
>     You will need to have vhostmd running on the oVirt node and set
>     the "sap_agent" custom property for the vm as you may see on the
>     screenshot.
>
>     sap_agent
>
>     Arsène
>
>     On 04/15/2016 12:15 PM, Simon Barrett wrote:
>
>         I’m trying to use the vhostmd vdsm host to access ovirt node
>         metrics from within a VM. Vhostmd is running and updating the
>         /dev/shm/vhostmd0 on the ovirt node.
>
>         The part I’m stuck on is: “This disk image is exported
>         read-only to guests. Guests can read the disk image to see
>         metrics” from
>         http://www.ovirt.org/develop/developer-guide/vdsm/hook/vhostmd/
>
>         Does the hook do this by default? I don’t see any new
>         read-only device mounted in the guest. Is there additional
>         work I need to do to mount this and access the data from
>         within the guest?
>
>         Many thanks,
>
>         Simon
>
>
>
>
>
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