[glue-wg] Update from ATLAS evaluation of GLUE2

[Paul Millar]

Hi all,

Here's a update from ATLAS' evaluation of GLUE2.

The process is ongoing and not yet finalised.  ATLAS is currently 
considering to take aspects of GLUE2 (trying to use the same attribute 
names, for example) but at the moment they are considering a format that 
would not be GLUE2 compliant.

The process has helped identify some sticking points, which I propose we 
should address.

Here are two concrete proposals that would help ATLAS:

   P1.	add a StorageShare attribute that describes the number of
	files stored in this StorageShare.  This should
	be optional (mult: 0..1).

   P2.	adjust multiplicity of StorageShare#Path to 0..*

The other issue they identified was that StorageShare doesn't store 
capacity information: that requires a whole new object (with IDs and 
linkage).

Here's a concrete proposal (so people can disagree :-) on how we can fix 
this:

   P3.	add the StorageShareCapacity usage metrics
	(TotalSize, FreeSize, UsedSize, ReservedSize) to
	StorageShare as optional attributes (mult: 0..1)

	These attributes MAY be used in situations where
	is clear which media is being used.  In such
	circumstances, the StorageShare SHOULD have at
	most one DataStore association.


   P4.	Rename StorageShareCapacity to DataStoreUsage,
	adding a required Association to a DataStore.

	This better reflects that StorageShareCapacity links
	a StorageShare to some corresponding hardware.

P1 and P2 are both rather trivial -- these should be fixed in GLUE v2.1.

P3 is also (technically) rather trivial -- if we want, this could go in 
GLUE v2.1

P4 would not be backwards compatible, so we would have to be a little 
careful how we roll it out.

Cheers,

Paul.