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Create an instance and boot from volume or image is better?

asked 2014-10-20 02:40:11 -0500

anhdenday gravatar image

Dear All, I have a question, when I create an instance should i boot it from volume or image? Which one is better? I am using CEPH backend storage. Thanks you so much

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answered 2014-10-20 02:54:51 -0500

jtaguinerd gravatar image


In our deployment, both glance and cinder are using ceph as the backend. From experience boot from volume is faster than boot from image. When we tried boot from image we have set libvirt_images_type=rbd, we noticed that the locally cached copy takes up additional 15-20 minutes, where it is being imported via the rbd import command.

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But I have a problem when create and boot from volume, whenever I create an instance from volume and image. If I create a snapshot from that instance so that it's will create an image not snapshot. You can check in the dashboard (in Admin/Images menu) at the field "type".

anhdenday gravatar imageanhdenday ( 2014-10-20 03:06:25 -0500 )edit

Hi, Like I said above, it is not a problem at all. That is just how it is.

jtaguinerd gravatar imagejtaguinerd ( 2014-10-20 08:48:24 -0500 )edit

answered 2014-10-20 03:12:45 -0500

anhdenday gravatar image

updated 2014-10-20 03:25:28 -0500

I have a problem with snapshot

After I create a instance that boot from both image and volume so that whenever I create snapshot from that instance the result is I got is not "snapshot" at type field, but I checked in "Volume" menu, at "Volume Snapshot" then see have volume snapshot here. Below is step that I create snapshot: 1- I have an instance name: anhdenday (this instance created from both image and volume)

2- I created a snapshot with name that "anhdenday_snapshot" 3 - I check in dashboard at "Admin/Image" and see that have image name that "anhdenday_snapshot" but type field is "Image" not "snapshot"

4- I also so check at "Project/Volumes/Volume Snapshot" and see that have a volume snapshot name is "snapshot for anhdenday_snapshot"

I wondering that the snapshot that i created with name "anhdenday_snapshot" why it have type "image" and the volume snapshot "snapshot for anhdenday_snapshot" is use for what purpose?

Finnally, I have a little bit confused is what the difference between the the disk (HDD) that I created when I choose from Flavor and the disk (Volume) that I created and boot from volume?

Thanks you so much

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It is correct that is shows as Image when you create a snapshot from an instance. To avoid the confusion, I would suggest, since you are using a bootable volume, to do a snapshot from the Volumes page not from the Instance page.

"snapshot for anhdenday_snapshot" is like rbd snapshot command in Ceph

jtaguinerd gravatar imagejtaguinerd ( 2014-10-20 08:45:38 -0500 )edit

For you final question, if you are using boot from volume the disk from the flavors is not being use at all, only the CPU and RAM.

jtaguinerd gravatar imagejtaguinerd ( 2014-10-20 08:46:44 -0500 )edit

Thanks you

anhdenday gravatar imageanhdenday ( 2014-10-22 04:25:56 -0500 )edit

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Asked: 2014-10-20 02:40:11 -0500

Seen: 3,985 times

Last updated: Oct 20 '14