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From "Fang Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CLOUDSTACK-732) Add back KVM snapshot support
Date Wed, 17 Jul 2013 21:05:46 GMT

    [ https://issues.apache.org/jira/browse/CLOUDSTACK-732?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13711623#comment-13711623
] 

Fang Wang commented on CLOUDSTACK-732:
--------------------------------------

For Cloudstack, vm snapshot and volume snapshot are two different mechanism. 
This feature is tracking the volume snapshot, or we could call it disk backup for cloudstack,
since it does disk backup.

Currently disk snapshot is not supported by cloudstack for KVM.

1. for 4.2, we will add a "KVM.snapshot.enabled" global flag under the "Global Settings" in
cloudstack UI;
the default value is "false" to turn off the snapshot, which is the current default behavior
without this flag;

2. If users want to turn on this flag, they need to install the new qemu rpm patch, and turn
on this flag;

3. for upgrade, if users did use this disk snapshot feature before upgrade, after the upgrade
to 4.2, the flag will be set to TRUE;
they then need to install the qemu patch;

4.. The qemu rpm patches will be submitted in a separate packaging patch.  Any suggestion
where we should put it? 
I am thinking of the "packaging" directory.

thanks.
                
> Add back KVM snapshot support
> -----------------------------
>
>                 Key: CLOUDSTACK-732
>                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-732
>             Project: CloudStack
>          Issue Type: Bug
>      Security Level: Public(Anyone can view this level - this is the default.) 
>          Components: KVM
>    Affects Versions: 4.0.0
>         Environment: RHEL 6.3
>            Reporter: edison su
>            Assignee: Fang Wang
>            Priority: Critical
>             Fix For: 4.2.0
>
>
> In the latest KVM(on both RHEL 6.3 and Ubuntu 12.04), it supports external snapshot.
We need to investigate the status of external snapshot, as far as I know, it still doesn't
support disk-only snapshot(taking snapshot will pause VM for a long time, e.g. few minutes).

> 1. testing external snapshot: take an external snapshot instead of default qcow2 internal
snapshot, then back it up into backup storage. Only need to test with libvirt snapshot API,
if it works, then works, no need to hack on the qemu-kvm.
> 2. test how long it will pause a VM during taking snapshot. from link [2] and [3], only
qemu-kvm-rhev supports disk-only snapshot, not sure ubuntu 12.04 supports it or not. We need
to investigate on the issue.
> If item 1 and item 2(disk-only snapshot) works, then we can support default kvm qcow2
snapshot again.
> The link: 
> [1] http://kashyapc.wordpress.com/2011/10/04/snapshotting-with-libvirt-for-qcow2-images/
> [2] http://www.linux-kvm.com/content/first-look-virtual-machine-online-disk-snapshots-coming-fedora-18
> [3] http://www.redhat.com/archives/libvir-list/2012-July/msg00782.html

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