[Starlingx-discuss] [StarlingX] Use Cinder generic image cache to replace raw caching

[Poncea, Ovidiu]

Hi Li,

Quick question: Is cache going to be freed when an image is deleted from glance? It would be a waste to cache images that are no longer needed.

Thanks,
Ovidiu
________________________________
From: Li, Xiaoyan [xiaoyan.li at intel.com]
Sent: Tuesday, November 13, 2018 9:19 AM
To: Rowsell, Brent; 'starlingx-discuss at lists.starlingx.io'
Subject: Re: [Starlingx-discuss] [StarlingX] Use Cinder generic image cache to replace raw caching

Hi,

About the raw cache function in StarlingX Cinder and Glance, I would like to remove it as Cinder has similar function. Please see following detail.
And if I  would like to remove the function in StarlingX, there are two methods:

1.       Submit a patch to revert the changes in Glance and Cinder.

2.       Ignore these patches during upgrading StarlingX/Cinder to new Cinder release.
Which way do we prefer to?

Best wishes
Lisa

From: Li, Xiaoyan
Sent: Thursday, September 20, 2018 10:17 AM
To: Rowsell, Brent <Brent.Rowsell at windriver.com>; starlingx-discuss at lists.starlingx.io
Subject: RE: [Starlingx-discuss] [StarlingX] Use Cinder generic image cache to replace raw caching


Hi, Brent



The following are mechanism of Cinder volume cache.



Creation of cached volume:

It creates a cached volume in the backend storage when creating from an image.

1.       Create_from_image:

https://github.com/openstack/cinder/blob/stable/pike/cinder/volume/flows/manager/create_volume.py#L890

2.       Return image cache entry: If not existed, it creates a new entry.

https://github.com/openstack/cinder/blob/stable/pike/cinder/volume/flows/manager/create_volume.py#L746

3.       Create a new image-volume and cache entry for it:

https://github.com/openstack/cinder/blob/stable/pike/cinder/volume/flows/manager/create_volume.py#L872



Use a cached volume when creating a volume:

https://github.com/openstack/cinder/blob/stable/pike/cinder/volume/flows/manager/create_volume.py#L723-L735



 Delete the cache volume: When capacity and number of cache entries exceed specified limit, it deletes cache entries (cached volumes).

https://github.com/openstack/cinder/blob/stable/pike/cinder/image/cache.py#L164

Best wishes
Lisa

From: Rowsell, Brent [mailto:Brent.Rowsell at windriver.com]
Sent: Thursday, September 6, 2018 10:02 AM
To: Li, Xiaoyan <xiaoyan.li at intel.com<mailto:xiaoyan.li at intel.com>>; starlingx-discuss at lists.starlingx.io<mailto:starlingx-discuss at lists.starlingx.io>
Subject: RE: [Starlingx-discuss] [StarlingX] Use Cinder generic image cache to replace raw caching

We would need to review this feature to ensure it provides equivalent functionality first.
If it does, great, we can look at reverting and enabling this cinder functionality.

Brent

From: Li, Xiaoyan [mailto:xiaoyan.li at intel.com]
Sent: Wednesday, September 5, 2018 9:59 PM
To: starlingx-discuss at lists.starlingx.io<mailto:starlingx-discuss at lists.starlingx.io>
Subject: [Starlingx-discuss] [StarlingX] Use Cinder generic image cache to replace raw caching

Hi all,

This email is about Raw caching function in StarlingX. This feature is to cache an image in backend storage like Ceph when we first create a volume in this backend storage.

In fact, Cinder upstream has already had a similar function in Pike release. https://specs.openstack.org/openstack/cinder-specs/specs/liberty/image-volume-cache.html
So I want to revert Raw caching function in StarlingX, and use Cinder generic image cache instead.
The problem is that we need to update Cinder config in StarlingX. Any comments?

Best wishes
Lisa



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