Open Stack

Ops, forgot references:
[1]
https://github.com/torvalds/linux/blob/1cc15701cd89b0ce695bbc5cff3a2bf3e2efd25f/include/uapi/linux/virtio_blk.h#L54
[2]
https://github.com/torvalds/linux/blob/1cc15701cd89b0ce695bbc5cff3a2bf3e2efd25f/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_
> Enterprise_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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