# SD1.2.5.1.2-B XIOS
# Background

XIOS, or XML-IO-Server, is a library dedicated to I/O management in climate codes targeted for large core simulation (> 10 000) on climate coupled models.

XIOS manages the output of diagnostics and other data produced by climate component codes into files and offers temporal and spatial post-processing operations on this data. 

XIOS aims at simplifying the I/O management by minimizing the number of subroutines to be called and by supporting a maximum of on-line processing of the data.

# Aim

  * To explore the use of XIOS to address three main challenges for climate data production:
    * Flexibility in management of I/O and data definition.
    * I/O performance.
    * Post-treatment.

# Outcomes

  * Describe the XIOS-XML terminology and structuration.
  * Test XIOS on a specific architecture.
  * Use one or more processes dedicated exclusively to the I/O management to obtain:
    * Simultaneous writing and computing by an asynchronous call.
    * Asynchronous transfer of data from clients to servers.
    * Asynchronous data writing by each server.
  * Use of parallel file system ability via Netcdf4-HDF5 file format to obtain:
    * Simultaneous writing in the same single file by all servers.
    * No more post-processing rebuilding of the files.

# Subskills