[occi-wg] Another proposal on Linking

[Alexander Papaspyrou]

Am 17.08.2010 um 14:09 schrieb Ralf Lyren:

>> I would really see some kind of resource (one of those you called "pseudo-resources") here. Of course, one would have to manage many more resource objects then...
> 
> Could you perhaps make an example of what this would look like using my disk-controller-example for instance?
> 
> I am afraid there could be several issues regarding the lifecycle of these additional resources. They have little meaning when the Link does not exist etc. Any special semantics implied when tying these resources together with Links is also somewhat unclear.

--8<-- snip --8<--
Let me take my favorite example again. We have:
- A Compute resource - in this case it is a Virtual Machine
- A Storage resource - in this case it is a shared disk for use with a cluster filesystem (e.g. GFS2)
Now we need to attach the disk to the virtual machine and in order to do so we must specify what disk controller interface/address the disk should appear on in the virtual machine. Let's say we want it to appear as an IDE drive on bus 1, unit 0 (hdc for Linux people).
--8<-- snap --8<--

resource::compute -> link -> resource::disk -> link -> resource::clusterfs

where disk is the "logical disk" that is plugged into the compute vm, and clusterfs is your shared disk/cluster filesystem. The former then would capture the interface/address stuff, and basically is a disk representation specifically for your compute VM.

From my point of view, especially for the VM use case, you have VMs and some kind of virtual storage, which is attached to it. This virtual storage may or may not be shared and, if necessary, can again rely upon other (physical or virtual) storage. There will be a layer of "virtual storage" anyway, since even if you attach physical storage directly to a VM, the representation of it within the VM is still a virtual disk.

After all, if you look at your typical NetApp ecosystem, the question whether a certain entity (disk, LUN, iSCSI target, you name it) is physical or virtual pretty much depends on the perspective...

Best,
Alexander

-- 
Alexander Papaspyrou
alexander.papaspyrou at tu-dortmund.de

-------------- next part --------------
A non-text attachment was scrubbed...
Name: Alexander Papaspyrou.vcf
Type: text/directory
Size: 498 bytes
Desc: not available
Url : http://www.ogf.org/pipermail/occi-wg/attachments/20100817/6f804a04/attachment.bin 
-------------- next part --------------

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 4678 bytes
Desc: not available
Url : http://www.ogf.org/pipermail/occi-wg/attachments/20100817/6f804a04/attachment-0001.bin