openPMD supports writing to and reading from ADIOS1
For this, the installed copy of openPMD must have been built with support for the ADIOS1 backend.
To build openPMD with support for ADIOS, use the CMake option
For further information, check out the installation guide,
build dependencies and the build options.
ADIOS1 has several staging methods for alternative file formats, yet natively writes to
We currently implement the
MPI_AGGREGATE transport method for MPI-parallel write (
POSIX for serial write) and
ADIOS_READ_METHOD_BP for read.
The following environment variables control ADIOS1 I/O behavior at runtime. Fine-tuning these is especially useful when running at large scale.
||Number of I/O aggregator nodes for ADIOS1
||Number of I/O OSTs for ADIOS1
||Online creation of the adios journal file (
Please refer to the ADIOS1 manual, section 6.1.5 for details.
Best Practice at Large Scale¶
A good practice at scale is to disable the online creation of the metadata file.
After writing the data, run
bpmeta on the (to-be-created) filename to generate the metadata file offline (repeat per iteration for file-based encoding).
This metadata file is needed for reading, while the actual heavy data resides in
<metadata filename>.dir/ directories.
Further options depend heavily on filesystem type, specific file striping, network infrastructure and available RAM on the aggregator nodes. If your filesystem exposes explicit object-storage-targets (OSTs), such as Lustre, try to set the number of OSTs to the maximum number available and allowed per job (e.g. non-full), assuming the number of writing MPI ranks is larger. A good number for aggregators is usually the number of contributing nodes divided by four.
For fine-tuning at extreme scale or for exotic systems, please refer to the ADIOS1 manual and talk to your filesystem admins and the ADIOS1 authors. Be aware that extreme-sale I/O is a research topic after all.
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