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From "Rajani Karuturi" <raj...@apache.org>
Subject Re: Review Request 28511: CLOUDSTACK-7412: Can't create proper template from VM on S3 secondary storage environment
Date Thu, 27 Nov 2014 11:30:47 GMT

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https://reviews.apache.org/r/28511/#review63211
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Ship it!


Ship It!

- Rajani Karuturi


On Nov. 27, 2014, 10:38 a.m., Hiroki Ohashi wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/28511/
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> 
> (Updated Nov. 27, 2014, 10:38 a.m.)
> 
> 
> Review request for cloudstack.
> 
> 
> Bugs: CLOUDSTACK-7412
>     https://issues.apache.org/jira/browse/CLOUDSTACK-7412
> 
> 
> Repository: cloudstack-git
> 
> 
> Description
> -------
> 
> [Abstract]
> 
> Root cause of this issue is a way to handle cache using S3 as
> Secondary Storage.
> 
> When CloudStack uploads a disk image on Primary Storage(PS) to
> Secondary Storage(SS), it caches the disk image on Secondary Staging
> Store(SSS). This is a bug.
> 
> CloudStack uses disk image cache every time if the cache exists. For
> this behavior, the old cache on SSS will be uploaded as a template
> though a CloudStack user creates the template from a newer disk image
> on PS than the cache.
> 
> So, we fixed this issue in a way that CloudStack deletes the cache on
> SSS after CloudStack uploads disk image to SS.
> 
> 
> [Details]
> 
> Process of handling cache is different between copy from SS to
> PS(download) and copy from PS to SS(upload).
> 
> * Downloading a disk image from SS to PS
> 
> This is the case that a CloudStack user creates an instance from a
> template. CloudStack caches the image on SSS.
> 
> * Uploading a disk image from PS to SS
> 
> This is the case that a CloudStack user creates a template from a disk
> image of an instance. CloudStack shouldn't cache a disk image because
> it usually happens that a cache image is older than a volume of an
> instance.
> 
> However, there is a bug in branch condition about post process of
> uploading a disk image. Then CloudStack doesn't delete the disk image
> on SSS.
> 
> CloudStack uses a common method to copy a disk image between PS and SS
> for upload and download. The method includes post process of disk
> image cache.
> 
> As a part of post process, it is judged whether a disk image on SSS is
> used as cache or not in this method:
> 
>   a. Delete a disk image as upload procedure
> 
>   b. Delete a disk image to handle errors
> 
>   c. Cache a disk image as download procedure
> 
> In case of uploading a disk image, branch-a should be selected. But
> branch-c is always selected by the condition bug. As a result, a disk
> image is left on SSS and used as cache next time a CloudStack user
> creates a template from an instance.
> 
> 
> Diffs
> -----
> 
>   engine/storage/datamotion/src/org/apache/cloudstack/storage/motion/AncientDataMotionStrategy.java
d6759cb 
> 
> Diff: https://reviews.apache.org/r/28511/diff/
> 
> 
> Testing
> -------
> 
> Items below are confirmed.
> 
> - A template created from an instance reflects a volume of the instance.
> - No cache file exists on NFS secondary staging store.
> - No cache entry exists on template_store_ref.
> 
> We use this patch in our environment.
> 
> 
> Thanks,
> 
> Hiroki Ohashi
> 
>


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