Logical storage units in VOSpace 1.1

[Matthew Graham]

Hi,

A request has from our friends at SDSC to include references to the 
actual storage units that data is being deposited on. The use case is 
data replication so, for example, I want to move/copy a data object from 
a slow tape archive to an ultrafast disk but both hardware units are 
within the same VOSpace or I want to retrieve a data object from the 
ultrafast disk copy and not the slow tape one.

I think that we can incorporate this easily into our existing data 
model. We will refer to hardware units as logical storage units with the 
implication that they are identified via a logical identifier (URI) that 
is set by the particular VOSpace implementation. To get the list of 
available storage units from a VOSpace, we will need a method: 
getLogicalStorageUnits() which will return a list of URIs. These URIs 
may be resolvable to a description of the storage unit.

The logical storage unit identifier will be an optional argument in the 
<transfer> entity so that as part of the data transfer negotiation, the 
user can specify a list of storage units that they want the data 
transferred to/from. The identifier will also be an optional argument in 
the <node> entity so that specific hardware can be targetted in moving 
and copying data.

Comments, suggestions, etc.

    Cheers,

    Matthew