Exnode specification: Difference between revisions

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[[Example L-Store xml file]]
[[Example L-Store xml file]]


exnodes and erasure codings.
 
== Erasure codings ==
*L-Store writes extra erasure allocations for allocation recovery.
*L-Store writes extra erasure allocations for allocation recovery.
**erasure allocations are also stored in the exnode file
**erasure allocations are also stored in the exnode file

Revision as of 20:54, 16 January 2008

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 are done in the data-management area, not the data-client.
  • user interface and development API are needed by the data client
    • The base exnode (LoRS)
  • command line tools
    • file movement
    • file system (some use the term namespace management) tools
      • list files, create directories, etc
  • C/C++ API
    • just need my simple offsets and lengths
    • would like to read a vector of data blocks (non-blocked reads)
    • don't want to deal with erasure stuff at this point.
      • is there a nice way to recover from errors?


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)