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Hi Duncan,

Thank you for the inputs.

@Community-Members
I want to know if there are any other alternatives to improve the performance of unshelve api ((booted from image only).
Please give me your opinion on the same.

Thank You,

Abhishek Kekane



From: Duncan Thomas [mailto:duncan.thomas at gmail.com]
Sent: 16 February 2015 16:46
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [nova] Unshelve Instance Performance Optimization Questions

There has been some talk in cinder meetings about making cinder<->glance interactions more efficient. They are already optimised in some deployments, e.g. ceph glance and ceph cinder, and some backends cache glance images so that many volumes created from the same image becomes very efficient. (search the meeting logs or channel logs for 'public snapshot' to get some entry points into the discussions)

I'd like to see more work done on this, and perhaps re-examine a cinder backend to glance. This would give some of what you're suggesting (particularly fast, low traffic un-shelve), and there is more that can be done to improve that performance, particularly if we can find a better performing generic CoW technology than QCOW2.
As suggested in the review, in the short term you might be better experimenting with moving to boot-from-volume instances if you have a suitable cinder deployed, since that gives you some of the performance improvements already.

On 16 February 2015 at 12:10, Kekane, Abhishek <Abhishek.Kekane at nttdata.com<mailto:Abhishek.Kekane at nttdata.com>> wrote:
Hi Devs,

Problem Statement: Performance and storage efficiency of shelving/unshelving instance booted from image is far worse than instance booted from volume.

When you unshelve hundreds of instances at the same time, instance spawning time varies and it mainly depends on the size of the instance snapshot and
the network speed between glance and nova servers.

If you have configured file store (shared storage) as a backend in Glance for storing images/snapshots, then it's possible to improve the performance of
unshelve instance dramatically by configuring nova.image.download.FileTransfer in nova. In this case, it simply copies the instance snapshot as if it is
stored on the local filesystem of the compute node. But then again in this case, it is observed the network traffic between shared storage servers and
nova increases enormously resulting in slow spawning of the instances.

I would like to gather some thoughts about how we can improve the performance of unshelve api (booted from image only) in terms of downloading large
size instance snapshots from glance.

I have proposed a nova-specs [1] to address this performance issue. Please take a look at it.

During the last nova mid-cycle summit, Michael Still<https://review.openstack.org/#/q/owner:mikal%2540stillhq.com+status:open,n,z> has suggested alternative solutions to tackle this issue.

Storage solutions like ceph (Software based) and NetApp (Hardare based) support exposing images from glance to nova-compute and cinder-volume with
copy in write feature. This way there will be no need to download the instance snapshot and unshelve api will be pretty faster than getting it
from glance.

Do you think the above performance issue should be handled in the OpenStack software as described in nova-specs [1] or storage solutions like
ceph/NetApp should be used in production environment? Apart from ceph/NetApp solutions, are there any other options available in the market.

[1] https://review.openstack.org/#/c/135387/

Thank You,

Abhishek Kekane

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Duncan Thomas

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