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HDF5 RADOS VOL connector

Table of Contents

  1. Description
  2. Installation
  3. Testing and Usage
  4. More information

1. Description

The HDF5 RADOS VOL connector is a Virtual Object Layer (VOL) connector for HDF5 that allows HDF5 applications to interface with object-, block- and file-based storage by using the RADOS API. It supports access to Ceph-based storage via librados and also supports access to Mobject-based storage.

The VOL connector is built as a plugin library that is external to HDF5 and can be loaded in an HDF5 application at runtime.

2. Installation

Prerequisites

To build the RADOS VOL connector, the following are required:

  • libhdf5 - The HDF5 library. Minimum version required is 1.13.3, compiled with support for parallel I/O.

  • An MPI library implementation

Additional dependencies are required, depending on which type of storage is of interest. If interested in accessing Mobject-based storage (the default mode of operation), the following are required:

If interested in accessing Ceph-based storage, the following are required:

Compiled libraries must either exist in the system's library paths or must be pointed to during the RADOS VOL connector build process. The simplest way to ensure these libraries can be located is to install and use them via spack.

For example, Mobject can be installed via spack according to the instructions listed in the project's README. Once installed, a simple

$ spack load mobject

should be sufficient for ensuring the Mobject libraries are available for the VOL connector build process.

Build instructions

The HDF5 RADOS VOL connector is built using CMake. CMake version 2.8.12.2 or greater is required for building the connector itself, but version 3.1 or greater is required to build the connector's tests.

After obtaining the connector's source code, you should first create a build directory within the source tree:

$ cd vol-rados
$ mkdir build
$ cd build

Then, if all of the required components are available, the connector can be built by using cmake (or ccmake):

$ cmake [cmake options] [connector options] ..
$ ccmake ..

If using cmake, then CMake options and options for the RADOS VOL connector should be passed on the command line with -D. If using ccmake, suitable options can be chosen in the interface. Some of these options may be needed if, for example, the required components mentioned previously are not located in default paths.

If using ccmake, setting include directory and library paths may require you to toggle to the advanced mode by typing 't'. Once all options have been chosen in the ccmake interface, you should type 'c' (this may need to be done multiple times as ccmake adjusts to settings chosen). Once you are done and do not see any errors, type 'g' to generate build files for the connector.

Once the project is configured via CMake, simply do:

$ make && make install

to build and install the connector plugin library. Note that this command may differ depending on the platform and CMake generator used.

CMake options

The following are some CMake options that may be desirable to set when building the RADOS VOL connector:

  • CMAKE_INSTALL_PREFIX - This option controls the install directory that the resulting output files are written to. The default value is /usr/local.
  • CMAKE_BUILD_TYPE - This option controls the type of build used for the VOL connector. Valid values are Release, Debug, RelWithDebInfo and MinSizeRel; the default build type is RelWithDebInfo.

Connector options

The following connector-specific CMake options are available when building the RADOS VOL connector:

  • HDF5_VOL_RADOS_USE_MOBJECT - This option specifies whether the VOL connector should be built with Mobject-based storage support. This is the default mode for the connector. If this option is disabled, the connector will instead be built with support for Ceph-based storage via librados.
  • BUILD_TESTING - This option is used to enable/disable building of the RADOS VOL connector's tests. The default value is OFF.
  • BUILD_EXAMPLES - This option is used to enable/disable building of the RADOS VOL connector's HDF5 examples. The default value is OFF.

3. Testing and Usage

The RADOS VOL connector contains no tests itself, but rather leverages the HDF5 VOL tests project for testing. Building of these tests is disabled by default, but can be enabled by setting the BUILD_TESTING option to ON.

For information on how to use the RADOS VOL connector with an HDF5 application, including setting up and running a Mobject or Ceph server, please refer to the RADOS VOL User's Guide under docs/users_guide.pdf.

4. More Information