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Accessing volumes in instance

asked 2013-06-25 19:14:22 -0500

Jay Forget gravatar image

updated 2013-06-25 19:35:43 -0500

Him very new to openstack. I did a ubuntu 12.04 installation fallowed directly by a Scripted Development Installation (just to see how openstack is) using the informations provided by this link : Everything is looking fine !!! I created a volume and i attached it to an instance(cirrOS) to /dev/vdx, but when i go into my instance i can't see or mount the volume because /dev/vdx is not present, i tried rebooting the instance but that did not make the change. Am i doing something wrong, or do i have a misunderstanding on how volumes work ? I looked in the documentation but nothing is said about how to use volumes in VM's. Thank you for your help, from a really interested noob.

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answered 2013-06-25 21:11:47 -0500

sgordon gravatar image

updated 2013-06-25 21:12:48 -0500

When you request a volume be attached to /dev/vdX what actually happens on all host Hypervisors except Xen is that the device is assigned to the next available letter in the guest - effectively the auto-assignment logic is always in effect.

What this means is practice is if your guest has a /dev/vda device already, and you request /dev/vdc, the device will actually be assigned to /dev/vdb in spite of your request. Perhaps this is why the volume is not where you expect it to be?

Note that you can also access the volumes using disk-by-id on recent versions of Cinder/Nova, so the volumes can be found at /dev/disk/by-id/virtio-ID where ID is replaced by a subset of the identifier of the volume as shown in the output of cinder list.

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Asked: 2013-06-25 19:14:22 -0500

Seen: 1,512 times

Last updated: Jun 25 '13