2012-12-20 23:18, Morrissey, Christopher:

Hi All,

I've been working on a bit of functionality for the engine that will allow a user to query a domain for new disk images (GetUnregisteredImagesQuery) for which the engine was previously unaware and a separate command to register those images (ImportImageCommand). These commands will be exposed through the REST API.

This functionality is needed as we are developing an extension/plugin to oVirt that will allow a NetApp storage controller to handle cloning the actual disks outside of oVirt and need to import them once they are cloned. We'll be using other existing APIs to attach the disk to the necessary VM once the disk is cloned. On the NetApp side, we'll ensure the disk is coalesced before cloning so as to avoid the issues of registering snapshots.

I am just curious about how the third party tool like NetApp to make sure the disk of a running VM coalesced before cloning? By an agent in the VM to flush file-system cache out to the disk?

GetUnregisteredImagesQuery will be accessible through the disks resource collection on a storage domain. A "disks" resource collection does not yet exist and will need to be added. To access the unregistered images, a parameter (maybe "unregistered=true") would be passed. So the path to "GET" the unregistered disk images on a domain would be something like /api/storagedomains/f0dbcb33-69d3-4899-9352-8e8a02f01bbd/disks?unregistered=true. This will return a list of disk images that can be each used as input to the ImportImageCommand to get them added to oVirt.

ImportImageCommand will be accessible through "POST"ing a disk to /api/disks?import=true. The disk will be added to the oVirt DB based on the information supplied and afterward would be available to attach to a VM.

When querying for unregistered disk images, the GetUnregisteredImagesQuery command will use the getImagesList() VDSM command. Currently this only reports the GUIDs of all disk images in a domain. I had been using the getVolumesList() and getVolumeInfo() VDSM commands to fill in the information so that valid disk image objects could be registered in oVirt. It seems these two functions are set to be removed since they are too invasive into the internal VDSM workings. The VDSM team will need to either return more information about each disk as part of the getImagesList() function or add a new function getImageInfo() that will give the same information for a given image GUID.

Here is the project proposal for floating disk in oVirt. I think unregistered images are also floating disks.

Note that much of this work had originally been submitted under patch http://gerrit.ovirt.org/#/c/9603/. After several reviews it was found to be lacking in its design and was using deprecated APIs that did not yet have replacements. I'm reworking the code now to conform to this design and asking for further input from the VDSM, core, and restapi teams to ensure we can get this done quickly and correctly as it is needed for the 3.2 release.


*Chris Morrissey*

Software Engineer

NetApp Inc.


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?? Shu Ming
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