[jira] [Commented] (CLOUDSTACK-7319) Copy Snapshot command too heavy on XenServer Dom0 resources when using dd to copy incremental snapshots

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    [ https://issues.apache.org/jira/browse/CLOUDSTACK-7319?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14224626#comment-14224626 ] 

ASF subversion and git services commented on CLOUDSTACK-7319:
-------------------------------------------------------------

Commit 7dbafba52f282e523f44de43a2328ccfeecc1e41 in cloudstack's branch refs/heads/4.3 from [~jvanlieshout@schubergphilis.com]
[ https://git-wip-us.apache.org/repos/asf?p=cloudstack.git;h=7dbafba ]

CLOUDSTACK-7319: dd with direct io is less impacting on Dom0 kernel resources

Signed-off-by: Daan Hoogland <da...@onecht.net>
(cherry picked from commit c4b78c3aaa8df20c8e892b9d5108d8f34f96ed0c)
(cherry picked from commit 37baddd7212717f259c33b3bb75720d718b92d2c)
Signed-off-by: Rohit Yadav <ro...@shapeblue.com>


> Copy Snapshot command too heavy on XenServer Dom0 resources when using dd to copy incremental snapshots
> -------------------------------------------------------------------------------------------------------
>
>                 Key: CLOUDSTACK-7319
>                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-7319
>             Project: CloudStack
>          Issue Type: Bug
>      Security Level: Public(Anyone can view this level - this is the default.) 
>          Components: Snapshot, XenServer
>    Affects Versions: 4.0.0, 4.0.1, 4.0.2, 4.1.0, 4.1.1, 4.2.0, Future, 4.2.1, 4.3.0, 4.4.0, 4.5.0, 4.3.1, 4.4.1
>            Reporter: Joris van Lieshout
>            Assignee: Brenn Oosterbaan
>            Priority: Critical
>             Fix For: 4.4.0
>
>
> We noticed that the dd process was way to agressive on Dom0 causing all kinds of problems on a xenserver with medium workloads. 
> ACS uses the dd command to copy incremental snapshots to secondary storage. This process is to heavy on Dom0 resources and even impacts DomU performance, and can even lead to domain freezes (including Dom0) of more then a minute. We've found that this is because the Dom0 kernel caches the read and write operations of dd.
> Some of the issues we have seen as a consequence of this are:
> - DomU performance/freezes
> - OVS freeze and not forwarding any traffic
> - Including LACPDUs resulting in the bond going down
> - keepalived heartbeat packets between RRVMs not being send/received resulting in flapping RRVM master state
> - Braking snapshot copy processes
> - the xenserver heartbeat script reaching it's timeout and fencing the server
> - poolmaster connection loss
> - ACS marking the host as down and fencing the instances even though they are still running on the origional host resulting in the same instance running on to hosts in one cluster
> - vhd corruption are a result of some of the issues mentioned above
> We've developed a patch on the xenserver scripts /etc/xapi.d/plugins/vmopsSnapshot that added the direct flag of both input and output files (iflag=direct oflag=direct).
> Our test have shown that Dom0 load during snapshot copy is way lower.



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