Open Stack

Yuk.   So looking back in the nova libvirt volume code, it looks like nova
is ignoring almost all of the device_info coming back from os-brick's
connect_volume() call.
os-brick has the scsi id  here:
https://github.com/openstack/os-brick/blob/master/os_brick/initiator/connectors/iscsi.py#L552

My guess is though, that nova uses the cinder UUID, in the domain xml so it
can use it later at some point?

Walt

On Wed, Jan 31, 2018 at 9:36 AM, Lucian Petrut <
lpetrut at cloudbasesolutions.com> wrote:

> Actually, when using the libvirt driver, the SCSI id returned by os-brick
> is not exposed to the guest. The reason is that Nova explicitly sets the
> volume id as "serial" id in the guest disk configuration. Qemu will expose
> this to the guest, but with a 20 character limit.
>
> For what is worth, Kubernetes as well as some guides rely on this
> behaviour.
>
> For example:
>
> nova volume-attach e03303e1-c20b-441c-b94a-724cb2469487
> 10780b60-ad70-479f-a612-14d03b1cc64d
> virsh dumpxml `nova show cirros | grep instance_name | cut -d "|" -f 3`
>
> <domain type='qemu' id='10'>
>   <name>instance-0000013d</name>
>   <uuid>e03303e1-c20b-441c-b94a-724cb2469487</uuid>
> ....
> <disk type='block' device='disk'>
>       <driver name='qemu' type='raw' cache='none' io='native'/>
>       <source dev='/dev/sdb'/>
>       <backingStore/>
>       <target dev='vdb' bus='virtio'/>
> *      <serial>10780b60-ad70-479f-a612-14d03b1cc64d</serial>*
>       <alias name='virtio-disk1'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x06'
> function='0x0'/>
>     </disk>
>
> nova log:
> Jan 31 15:39:54 ubuntu nova-compute[46142]: DEBUG
> os_brick.initiator.connectors.iscsi [None req-d0c62440-133c-4e89-8798-20278ca50f00
> admin admin] <== connect_volume: return (2578ms) {'path': u'/dev/sdb',
> 'scsi_wwn': u'360000000000000000e00000000010001', 'type': u'block'}
> {{(pid=46142) trace_logging_wrapper /usr/local/lib/python2.7/dist-
> packages/os_brick/utils.py:170}}
> Jan 31 15:39:54 ubuntu nova-compute[46142]: DEBUG
> nova.virt.libvirt.volume.iscsi [None req-d0c62440-133c-4e89-8798-20278ca50f00
> admin admin] Attached iSCSI volume {'path': u'/dev/sdb', 'scsi_wwn': '
> 360000000000000000e00000000010001', 'type': 'block'} {{(pid=46142)
> connect_volume /opt/stack/nova/nova/virt/libvirt/volume/iscsi.py:65}}
> Jan 31 15:39:54 ubuntu nova-compute[46142]: DEBUG nova.virt.libvirt.guest
> [None req-d0c62440-133c-4e89-8798-20278ca50f00 admin admin] attach device
> xml: <disk type="block" device="disk">
> Jan 31 15:39:54 ubuntu nova-compute[46142]:   <driver name="qemu"
> type="raw" cache="none" io="native"/>
> Jan 31 15:39:54 ubuntu nova-compute[46142]:   <source dev="/dev/sdb"/>
> Jan 31 15:39:54 ubuntu nova-compute[46142]:   <target bus="virtio"
> dev="vdb"/>
> Jan 31 15:39:54 ubuntu nova-compute[46142]:   <serial>10780b60-ad70-479f-
> a612-14d03b1cc64d</serial>
> Jan 31 15:39:54 ubuntu nova-compute[46142]: </disk>
> Jan 31 15:39:54 ubuntu nova-compute[46142]:  {{(pid=46142) attach_device
> /opt/stack/nova/nova/virt/libvirt/guest.py:302}}
>
> Regards,
> Lucian Petrut
>
> On Wed, 2018-01-31 at 07:59 -0500, Walter Boring wrote:
>
> First off, the id's you are showing there are Cinder uuid's to identify
> the volumes in the cinder DB and are used for cinder based actions.  The
> Ids that are seen and used by the system for discovery and passing to qemu
> are the disk SCSI ids, which are embedded in the volume's themselves.
> os-brick returns the SCSI id to nova for use in attaching and it's not
> limited to the 20 characters.
>
>
>
> On Tue, Jan 16, 2018 at 4:19 AM, Yikun Jiang <yikunkero at gmail.com> wrote:
>
> Some detail steps as below:
> 1. First, We have 2 volumes with same part-uuid prefix.
> [image: 内嵌图片 1]
>
> volume(yikun2) is attached to server(test)
>
> 2. In GuestOS(Cent OS 7), take a look at by path and by id:
> [image: 内嵌图片 2]
> we found both by-path and by-id vdb links was generated successfully.
>
> 3. attach volume(yikun2_1) to server(test)
> [image: 内嵌图片 4]
>
> 4. In GuestOS(Cent OS 7), take a look at by path and by id:
>
> [image: 内嵌图片 6]
>
> by-path soft link was generated successfully, but by-id link was failed
> to generate.
> *That is, in this case, if a user find the device by by-id, it would be
> failed to find it or find a wrong device.*
>
> one of the user cases was happened on k8s device finding, more info you
> can see the ref as below:
> https://github.com/kubernetes/kubernetes/blob/53a8ac753bf468
> eaf6bcb5a07e34a0a67480df43/pkg/cloudprovider/providers/
> openstack/openstack_volumes.go#L463
>
> So, I think by-id is NOT a good way to find the device, but what the best
> practice is? let's see other idea.
>
> Regards,
> Yikun
>
> ----------------------------------------
> Jiang Yikun（Kero）
> Mail: yikunkero at gmail.com
>
> 2018-01-16 14:36 GMT+08:00 Zhenyu Zheng <zhengzhenyulixi at gmail.com>:
>
> Ops, forgot references:
> [1] https://github.com/torvalds/linux/blob/1cc15701cd89b0ce6
> 95bbc5cff3a2bf3e2efd25f/include/uapi/linux/virtio_blk.h#L54
> [2] https://github.com/torvalds/linux/blob/1cc15701cd89b0ce6
> 95bbc5cff3a2bf3e2efd25f/drivers/block/virtio_blk.c#L363
>
> On Tue, Jan 16, 2018 at 2:35 PM, Zhenyu Zheng <zhengzhenyulixi at gmail.com>
> wrote:
>
> Hi,
>
> I meet a problem like this recently:
>
> When attaching a volume to an instance, in the xml, the disk is described
> as:
>
> [image: Inline image 1]
> where the serial number here is the volume uuid in Cinder. While inside
> the vm:
> in /dev/disk/by-id, there is a link for /vdb with the name of
> "virtio"+truncated serial number:
>
> [image: Inline image 2]
>
> and according to https://access.redhat.com/documentation/en-US/Red_Hat_Ent
> erprise_Linux_OpenStack_Platform/2/html/Getting_Started_Guide/ch16s03.html
>
> it seems that we will use this mount the volume.
>
> The truncate seems to be happen in here [1][2] which is 20 digits.
>
> *My question here is: *if two volume have the identical first 20 digits
> in their uuids, it seems that the latter attached one will overwrite the
> first one's link:
> [image: Inline image 3]
> (the above graph is snapshot for an volume backed instance, the
> virtio-15exxxxx was point to vda before, the by-path seems correct though)
>
> It is rare to have the identical first 20 digits of two uuids, but
> possible, so what was the consideration of truncate only 20 digits of the
> volume uuid instead of use full 32?
>
> BR,
>
> Kevin Zheng
>
>
>
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