[libvirt] question about syntax of storage volume <target> element

[Cole Robinson]

On 09/28/2018 12:54 AM, Jim Fehlig wrote:
> I've attempted to use virt-manager to create a new VM that uses a volume 
> from an rbd-based network pool, but have not been able to progress past 
> step 4/5 where VM storage is selected. It appears virt-manager has 
> problems properly detecting the volume as network-based storage, but 
> before investigating those further I have a question about the syntax of 
> the <target> element of a storage volume.

Yeah virt-manager is known to be lacking WRT rbd. I did some work a few 
years back but didn't finish it. At least it doesn't know how to 
correctly use a volume with any auth data in the XML. I need to get 
another rbd setup to test with and fix it all

  The storage management page
> [0] of the website describing rbd volumes claims that the <path> 
> subelement contains an 'rbd:rbd/' prefix in the volume path. But the 
> page describing pool and volume format [1] syntax does not contain any 
> info wrt specifying network URLs in the <path> subelement.
> 
> What is the expectation wrt the <path> subelement of the <target> 
> element within rbd volume config? In general, should the <path> 
> subelement encode the scheme (e.g. rbd://) of a network-based volume? 
> And if so, should it be formatted in the traditional 'rbd://' vs 
> 'rbd:rbd/' syntax?
> 

I noticed this too. sheepdog is weird as well. Gluster has full URIs in 
the volume <path> though

I certainly think full URIs is the way it should be... even if nothing 
natively handles the URI format we output, I think a <path> field should 
be fully descriptive/unique, like how file volumes in directory pools 
show absolute paths.

I guess the question though is if we can change it at this point, it's 
been like that for years, apps may be depending on the weird format in 
someway

- Cole