Exnode specification

The exnode specification is implied by current usage in L-Store and LoRS.

Example LoRS exnode xml file

Example L-Store xml file

Erasure codings

• L-Store writes extra erasure allocations for allocation recovery.
  • erasure allocations are also stored in the exnode file
  • erasure allocations are only useful to the data-management area and not the data-client
  • erasure allocations constitute an extension of the base (LoRS) exnode concept (or schema)
• L-Store can write a LoRS compatible exnode file that excludes the erasure allocations.
  • LoRS compatible (the base schema)
  • LoRS does not have access to L-Store's capability to recover an allocation
• The L-Store data-client (Lstcp) has no allocation recovery capability.
• data recovery, data warming, etc all data-management tasks, not data-client task.

Data client API & interfaces

• command line tools for file management
  • list files, create directories, etc
• LoRS API
  • uses the base exnode (LoRS)
  • reads local exnode files
  • talks to LoDN with a combined http:/LoDN protocol
  • C/C++ Posix and posix-like API
• Lstcp API (not developed yet)
  • does not use exnodes
  • talks to L-Server with the L-Store protocol
• typical C/C++ API needs (proposed)
  • simple offsets and lengths
  • non-blocked (vector) reads

Schema

The exnode xml is fairly unstructured and the functionality of a schema is minimal.

Simplified xml file

• (removed xmlns to view structure more clearly)

Simple schema

• The schema shows that only the element mapping has much structure.
• The element metadata's use of attributes is completely open.
• The only re-used type is the IBP_capability (read,write,manage)