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https://issues.apache.org/jira/browse/CLOUDSTACK-9733?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15811629#comment-15811629
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ASF GitHub Bot commented on CLOUDSTACK-9733:
--------------------------------------------

GitHub user sureshanaparti opened a pull request:

    https://github.com/apache/cloudstack/pull/1897

    CLOUDSTACK-9733: Concurrent volume snapshots of a VM are not allowed and 
are not limited per host as per the global configuration parameter 
"concurrent.snapshots.threshold.perhost".

    - User can take snapshots of the volumes attached to a VM simultaneously 
(when the underlying hypervisor supports). Only subsequent snapshot operations 
are in parallel.
    - User wants to take snapshots of the same volume at the same time (either 
recurring mode or manually). Only subsequent snapshot operations are in 
parallel.
    - User wants to limit the no. of concurrent snapshots per host in the 
cluster/cloud using the config paramter 
"concurrent.snapshots.threshold.perhost" (at the cluster level).

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/Accelerite/cloudstack CLOUDSTACK-9733

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/cloudstack/pull/1897.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #1897
    
----
commit 46d79f1678399cbd884973358504a2773a61abaf
Author: Suresh Kumar Anaparti <[email protected]>
Date:   2017-01-09T11:59:48Z

    CLOUDSTACK-9733: Concurrent volume snapshots of a VM are not allowed and 
are not limited per host as per the global configuration parameter 
"concurrent.snapshots.threshold.perhost".

----


> Concurrent volume snapshots of a VM are not allowed and are not limited per 
> host as per the global configuration parameter 
> "concurrent.snapshots.threshold.perhost".
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CLOUDSTACK-9733
>                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-9733
>             Project: CloudStack
>          Issue Type: Bug
>      Security Level: Public(Anyone can view this level - this is the 
> default.) 
>          Components: Snapshot, Volumes
>            Reporter: Suresh Kumar Anaparti
>            Assignee: Suresh Kumar Anaparti
>             Fix For: 4.10.0.0
>
>
> Pre-CloudStack 4.4.0, before the VM job framework changes (CLOUDSTACK-669), 
> Concurrent volume (both root and data) snapshots were allowed per host based 
> on the value of global config "concurrent.snapshots.threshold.perhost". The 
> volumes could belong to the same VM or spread across multiple VMs on a given 
> host. The synchronisation was done based on the host (Id).
> As part of the VM job framework changes (CLOUDSTACK-669) in CloudStack 4.4.0, 
> a separate job queue was introduced for individual VMs with a concurrency 
> level of 1 (i.e. all operations to a given VM are serialized). Volume 
> snapshot was also considered as a VM operation as part of these changes  and 
> goes through the VM job queue. These changes made the config 
> "concurrent.snapshots.threshold.perhost" obsolete (it was also no longer 
> getting honoured, since there is no single point of enforcement).
> Only one volume snapshot of a VM is allowed at any given point of time as the 
> sync object is the VM (id). So concurrent volume snapshots of a VM are not 
> allowed and are not limited per host as per the global configuration 
> parameter "concurrent.snapshots.threshold.perhost".
> This functionality needs to be re-introduced to execute more than 1 snapshot 
> of a VM at a time (when the underlying hypervisor supports) and snapshots 
> should be limited per host based on the value of 
> "concurrent.snapshots.threshold.perhost" at the cluster level (for more 
> flexibility).



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