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

[Doug Goldstein <cardoe@xxxxxxxxxx>]

On 1/27/16 12:32 PM, 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 libxl would need to understand the new 'target=' blob to parse it out?
> 

libvirt would probably just do what its doing now. Since it can setup
the connection and pass the file descriptor into libxl. Honestly I don't
see the advantage here because libvirt does a better job from a security
standpoint and unless the goal is to have everything and the kitchen
sink in libxl/xl. There's already a number of ways to skin the cat (xl,
libvirt, xapi, openstack), why another one?

-- 
Doug Goldstein

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