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How to view/list root disks if they are not in cinder?

asked 2018-11-20 09:57:22 -0500

frantisek gravatar image

updated 2018-11-21 08:28:16 -0500

If server is created with 'image' as Boot Source and for Create New Volume 'No' is selected then boot volume of the server is not created via Cinder but via Nova. It is not visible via cinder API. How do I list/view such a volume via OpenStack API?

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answered 2018-11-20 11:46:08 -0500

It is not a volume, but ephemeral storage, and can’t be listed separately from the instance.

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Are you saying that it is openstack resource which can be created but can not be viewed/listed via API? I believe OpenStack is following API driven aproach, so creating resource via API that I am not able to see via API seems unfortunate.

frantisek gravatar imagefrantisek ( 2018-11-20 15:54:16 -0500 )edit

It can't be viewed or listed, and it can't be created either. There is no API for ephemeral storage.

Or: It can be created, viewed or listed by creating, viewing or listing the instance that uses it.

Bernd Bausch gravatar imageBernd Bausch ( 2018-11-20 16:25:01 -0500 )edit

See it this way. Like CPU or RAM, ephemeral storage doesn't exist on its own. It's part of an instance. It doesn't have an ID, it is created and removed together with the instance. A volume, on the other hand, is an independent resource with an ID and an API.

Bernd Bausch gravatar imageBernd Bausch ( 2018-11-20 16:35:34 -0500 )edit

Can you get the size of such a disk from compute API then? What I have found is flavor.ephemeral but it just takes value from flavor disk and that can be 0 which is obviously wrong.

frantisek gravatar imagefrantisek ( 2018-11-21 04:08:09 -0500 )edit

Well, if the flavor specifies a disk size of 0, the disk should have a size of 0 I would think. Why should the disk’s size differ from the flavor?

A flavor with disk size 0 can be used for a diskless instance or an instance that boots from volume.

Bernd Bausch gravatar imageBernd Bausch ( 2018-11-21 16:20:41 -0500 )edit
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answered 2018-11-20 15:21:28 -0500

yasin lachiny gravatar image

You can find them in

/var/lib/nova/instances It is not volume you build them on flavor

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Thank you, but he question was: "How do I list/view such a volume via OpenStack API?" - I need to use API.

frantisek gravatar imagefrantisek ( 2018-11-20 15:54:14 -0500 )edit
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answered 2018-11-22 09:04:13 -0500

frantisek gravatar image

Unfortunately nova can be configured in a way that enables nova API to create ephemeral root volume with size that is not limited/determined by flavor but it provides no way how to view such a root disk. Telemetry API may be able to provide info on such a disk including size.

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Asked: 2018-11-20 09:57:22 -0500

Seen: 569 times

Last updated: Nov 22 '18