Ask Your Question

error launch instance / fail creating instance

asked 2018-02-08 12:36:22 -0500

finch15 gravatar image

Hi there, I am experiencing a common issue, that of not being able to create a new instance. I believe it has to do with disk space of some sort. This is the cinder volume size:

  PV         VG             Fmt  Attr PSize    PFree

 /dev/loop1 cinder-volumes lvm2 a--   <30.90g 920.00m

i have previously installed openstack and worked fine. not sure what's wrong this time. Thanks in advance for helping out.

edit retag flag offensive close merge delete

2 answers

Sort by » oldest newest most voted

answered 2018-02-14 05:44:24 -0500

updated 2018-02-14 19:01:24 -0500

Since your disk space for volumes is lower than the minimum volume size of 1GB, you can’t create any more volumes. If you launch instances with a volume as root disk (that’s the default if you use the GUI), this must fail.

Suggestions: Provide more space for volumes, or launch instances without volumes.

If instances without volumes can’t be launched, the problem is elsewhere. In this case, post error details and log messages.

EDIT: Instances can use so-called ephemeral storage, which disappears when the instance is deleted. In this case, their root disk is located on the compute node's filesystem, usually in the form of a file such as a qcow2 file. The size of an instance's ephemeral root disk is defined by the flavour.

You say that launching an instance with ephemeral storage fails. This means that something else is amiss; perhaps you simply don't have enough disk space or the compute node is lacking other resources like RAM.

Alternatively, an instance can use permanent storage in the form of a Cinder volume.

As I said before, when you launch an instance from Horizon, by default permanent storage is selected. You can change that with a switch in the instance launch dialog. On the other hand, when you use the CLI, the default is ephemeral storage; see

Of course, Cinder can be extended. You can, for example, add a backend. You seem to be using DevStack or PackStack to deploy your cloud; these deployment tools create a small LVM volume group on a loopback disk as their sole Cinder backend. I suppose that they have options for sizing this disk; personally, I have never tried increasing the size on a runnning DevStack or PackStack, but it should be possible by:

  1. increasing the size of the disk file that underlies your loopback disk. The fallocate command may be able to do that.
  2. adapting the size of the physical volume with the pvresize command.

It's probably easier, and teaches you more about OpenStack rather than Linux administration, to add a backend. This should be documented at

Or find out with what option you can specify the Cinder backend size and redeploy your cloud from scratch.

edit flag offensive delete link more


Hi Bernd, what is the difference between attaching a volume and the one that comes with the Flavour setting when Launching Instance (Total Disk & Root Disk) please?

With out Attaching a Volume, I couldn't install any OS as the installation could not detect any disks.

Is Cinder Volume extendable?

finch15 gravatar imagefinch15 ( 2018-02-14 15:29:13 -0500 )edit

I added some text to my answer.

Bernd Bausch gravatar imageBernd Bausch ( 2018-02-14 18:59:53 -0500 )edit

answered 2018-02-13 23:38:12 -0500

Deepa gravatar image

What is the error message you are receiving in nova logs ?

edit flag offensive delete link more

Get to know Ask OpenStack

Resources for moderators

Question Tools

1 follower


Asked: 2018-02-08 12:36:22 -0500

Seen: 1,989 times

Last updated: Feb 14 '18