@@ -128,8 +128,8 @@ The idea to provide scientific communities or individuals with the ability to sp
\subsection{Caching within XDC}
In this section we consider how the XDC architecture treats the storage and access of data, building a hierarchy of components whose goal is to maximise the accessibility of data to clients while minimising global infrastructure costs. The architecture considers a set of multi-site storage systems, potentially accessed through caches, both of which are aggregated globally through a federation.
While large, multi-site storage systems may hold the majority of a community custodial data, XDC does not foresee that they will necessarily host all the compute capacity. In particular, CPU-only resource centres or cloud procurements must be supported. Provision must therefore be made to ensure wide area data access is as efficient as possible.
Such resource centres may access custodial data through a standalone proxy cache. The simplest cache envisaged by XDC, a kind of "minimum viable product", would have the
While large, multi-site storage systems may hold the majority of a community custodial data, XDC does not foresee that they will necessarily host all the compute capacity. In particular, CPU-only resource centers or cloud procurements must be supported. Provision must therefore be made to ensure wide area data access is as efficient as possible.
Such resource centers may access custodial data through a standalone proxy cache. The simplest cache envisaged by XDC, a kind of "minimum viable product", would have the
following characteristics: Read-only operation, Fetch data on miss with service credentials, Data can be chunked or full-file, Manage cache residency, evicting data when necessary, HTTP frontend with group-level authorisation. Beyond this scenario, certain extensions will be investigated: Write support, Synchronisation and enforcement of ACLs, Namespace synchronisation (allowing discovery of non-resident data), Call-out to FTS for data transport, QoS support, Integration with notifications, such as primary storage notifying a file deletion
To such purpose, various technologies are available to the project to serve as the basis of an implementation:
