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 <[email protected]> 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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