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Re: [Xen-devel] [RFC] support more qdisk types

On 01/27/2016 11:32 AM, Konrad Rzeszutek Wilk wrote:
> On Mon, Jan 25, 2016 at 05:25:02PM -0700, Jim Fehlig wrote:
>> I would like to hear the community's opinion on supporting more qdisk types 
>> in
>> xl/libxl, e.g. nbd, rbd, iSCSI, etc. I prefer supporting additional qdisk 
>> types
>> in libxl over apps like xl or libvirt doing all the setup, producing a block
>> device, and then passing that to libxl. Each libxl app would have to
>> re-implement functionality already provided by qdisk. libxl already supports
>> IDE, AHCI, SCSI, and Xen PV qdisks. My suggestion is to extend that to 
>> initially
>> include nbd, rbd, and iSCSI. Sheepdog, ssh, etc. could be added in the 
>> future.
> ssh?


>> I considered several approaches to supporting additional qdisk types, based
>> primarily on changes to the disk cfg and interface. At one extreme is to 
>> change
>> nothing and use the existing 'target=' to encode all required config for the
>> additional qdisk types. libxl would need to be taught how to turn the blob 
>> into
>> an appropriate qdisk. At the other extreme is extending xl-disk-configuration
> Either way - new backends would require changes in both libxl and libvirt 
> right?

The backend is not new, it's qdisk. I'm suggesting to support more qdisk types.
But yes, it requires changes to libxl, xl, and libvirt.

> The libxl would need to understand the new 'target=' blob to parse it out?

Right, that's one approach. The config info is encoded in 'target=' in a
specified format, and libxl parses it out. Another approach is libxl provides
more settings for specifying these qdisk types.


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