...

The MARS client is a C program linked with GRIB API and the EMOSLIB library (which contains the GRIB interpolation software)with ECC, to handle GRIB and BUFR data, and the MIR package, to support interpolation and regridding operations. The MARS source code is also embedded in other applications, such as Metview.

...

Most of the access from Member State users comes via the ecgate system, by logging in or submitting batch jobs to ECMWF's computers. Moreover, the MARS client software is also available to access ECMWF's MARS archive system remotely by installing it at Member State sites. It removes user's need to login. Access and transfer of the data is transparent to the user, although data transfer may be slow. In addition, it is possible to create secondary cache systems at Member State sites in order to minimise remote access and transfer for popular data.

Servers

Reports Data Base

The RDB Contains online observations received via ECMWF's acquisition system. This system has been interfaced with MARS to allow real-time observation access. Access to this server is meant for monitoring and operational archive purpose only.

Fields Data Base (FDB)

This is where models running at ECMWF write their outputs. It contains data produced by the most recent cycles.

Depending on the configuration and disk resources, it can contain up to several days of operational data and more recent research experiments. Also, there are many Fields Databases, several per supercomputer or server able to run ECMWF's models.

ECMWF Web API service allows authorised users to retrieve and list MARS data from outside ECMWF and to transfer the data directly to their host.

Servers

Details about the architecture of the MARS server are given in a separate article. MARS has evolved since this article was written back in 1999, e.g., software developed at ECMWF has replaced ObjectStore as metadata manager, but the general architecture is still valid. In 2003, the MARS contents were migrated to the High Performance Storage System (HPSS) tape management software, which replaced Tivoli Storage Manager (TSM, previously known as ADSM).

The various servers are described below.It is meant to provide very fast access as all the data resides online. This makes it very suitable for model input data retrieval or last cycles data access.

Main Archive

This is the core of the MARS System and consists of the following hardware and software:

...

• A set of applications written in C++ linked with the EMOSLIB libraryMIR and ecCodes libraries
• High Performance Storage System (HPSS), which controls the tape, tape drive and robotic related activities.

Some characteristics of the Main Archive main archive system such as request scheduling and data collocation are very important for users in order to optimise data retrieval.

Fields Data Base (FDB)

This is where models running at ECMWF write their outputs. It contains data produced by the most recent cycles.

Depending on the configuration and disk resources, it can contain up to several days of operational data and more recent research experiments. Also, there are many Fields Databases, several per supercomputer or server able to run ECMWF's models.

It is meant to provide very fast access as all the data resides online. This makes it very suitable for model input data retrieval or last cycles data access.

Reports Data Base

The RDB Contains online observations received via ECMWF's acquisition system. This system has been interfaced with MARS to allow real-time observation access. Access to this server is meant for monitoring and operational archive purpose only.

Interaction client/server: request execution

...

Note that post-processing is done while the data is being transferred and before writing to disk.