Update README.md

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## Software requirements

## Overview

Compiling and running `scord` requires up-to-date versions of various software

packages. Beware that using excessively old versions of these packages can

Scord is an open-source storage coordination service designed for Linux HPC

clusters. As a storage coordination service, Scord provides facilities for

system administrators to easily model their storage hierarchies and expose them

to users in a consistent manner. Once the storage architecture is modelled,

Scord can efficiently orchestrate data transfers between the different

storage tiers in order to support complex HPC workloads using node-local

storage, burst buffers and ad-hoc storage systems.

> **ℹ️** **Important**  

> This software was partially supported by the EuroHPC-funded project ADMIRE  

   (Project ID: 956748, https://www.admire-eurohpc.eu).

## Building and installing

This section describes how to build and install Scord. Two main options

are basically supported out of the box:

- Automatically building both Scord and its dependencies using

  [Spack](https://github.com/spack/spack).

- Build and install Scord manually.

### Building scord and its dependencies with Spack

Scord and all its dependencies can be built using

[Spack](https://github.com/spack/spack). If you already have Spack, make sure

you have the latest release. If you use a clone of the Spack `develop`

branch, be sure to pull the latest changes.

#### Installing Spack

If you haven't already, install Spack with the following commands:

```shell

$ git clone -c feature.manyFiles=true https://github.com/spack/spack

```

This will create a directory called `spack` in your machine. Once you have

cloned Spack, we recommend sourcing the appropriate script for your shell.

This will add Spack to your `PATH` and enable the use of the `spack` command:

```shell

# For bash/zsh/sh

$ . spack/share/spack/setup-env.sh

# For tcsh/csh

$ source spack/share/spack/setup-env.csh

# For fish

$ . spack/share/spack/setup-env.fish

```

Since Scord is not yet available in the official Spack repositories, you need

to add the Scord Spack repository to the local Spack namespace in your

machine. To do so, download the

[`spack/` directory](https://storage.bsc.es/gitlab/eu/admire/io-scheduler/-/tree/main/spack)

located in the root of Scord's repository root to your machine (e.g. under

`~/projects/scord/spack`) and execute the following:

```shell

spack repo add ~/projects/scord/spack/

```

You should now be able to fetch information from the Scord package using

Spack:

```shell

spack info scord

```

If that worked, you are now ready to install Scord:

```shell

spack install scord

```

You can include or remove variants with Spack when a custom Scord

build is desired. The available variants are listed below:

| Variant | Command     | Default | Description                                                              |

|---------|-------------|---------|--------------------------------------------------------------------------|

| OFI     | `scord+ofi` | True    | Use [libfabric](https://github.com/ofiwg/libfabric) as transport library |

| UCX     | `scord+ucx` | False   | Use [ucx](https://github.com/openucx/ucx.git) as transport library       |

> ⚠️ **Attention**  

> The initial install could take a while as Spack will install build

> dependencies (autoconf, automake, m4, libtool, pkg-config, etc.) as well as

> any dependencies of dependencies (cmake, perl, etc.) if you don’t already

> have these dependencies installed through Spack.

After the installation completes, remember that you first need to load

Scord in order to use it:

```shell

spack load scord

```

### Building scord manually

If you prefer to build and install Scord from sources, you can also do so

but bear in mind that compiling and running Scord requires up-to-date

versions of various software packages that will need to be available in your

system. Also beware that using excessively old versions of these packages can

cause indirect errors that are very difficult to track down.

The following software packages are required to build `scord` and need to be

available in the system:

With that in mind, the following software packages are required to build Scord

and need to be available in the system:

- A C++ compiler that supports the C++20 standard, for example

[GCC](https://gcc.gnu.org)/[Clang](https://clang.llvm.org/) versions

8.0/5.0 or later.

8.0/6.0 or later.

- [CMake](https://cmake.org) 3.19 or later.

- pkg-config 0.29.1 (earlier versions will probably work but haven't been tested).

- [yaml-cpp](https://github.com/jbeder/yaml-cpp) version 0.6.2 and later.

3 or later, and its dependencies:

  - [hiredis](https://github.com/redis/hiredis) version 0.14.1 or later.

The following libraries are also required by `scord`, but will be

The following libraries are also required by Scord, but will be

automatically downloaded and compiled by the project as part of the standard

build process.

> **ℹ️** **Important**  

Margo and Argobots use `pkg-config` to ensure they compile and link correctly

with all of their dependencies' libraries. When building `scord` manually,

with all of their dependencies' libraries. When building Scord manually,

you'll need to appropriately set either the ``PKG_CONFIG_PATH`` environment

variable or the ``CMAKE_PREFIX_PATH`` CMake variable to the appropriate

installation paths where the ``.pc`` files for Argobots and Margo reside.

## Building

#### Building

You may either install the full sources or clone the repository directly. The

package relies on CMake to build the service, which requires you to do an

out-of-source build. Thus, once the `scord` sources are located in an

out-of-source build. Thus, once the Scord sources are located in an

appropriate `SCORD_SOURCES` directory (for example, `$HOME/scord`), you can

build the service by running the following commands:

make

```

### A more complex example:

#### A more complex example:

The following CMake options can be used to configure how `scord` is built:

The following CMake options can be used to configure how Scord is built:

- `SCORD_TRANSPORT_LIBRARY`: This option allows configuring the transport

  library used by the service. Currently, both `libfabric` and `ucx` are

- `SCORD_BUILD_TESTS`: This option instructs CMake to build the tests

  contained in the `tests` subdirectory.

Thus, let's assume that we want to build `scord` with the following

Thus, let's assume that we want to build Scord with the following

configuration:

1. The service should use `libfabric` as the transport library.

2. The service should use `tcp` as the communication protocol.

3. The server should listen for RPCs on address `192.168.0.111` and on port

   `52000`.

5. Usage examples should be built.

4. Usage examples should be built.

Let's also assume that `scord` sources are located in `$HOME/scord`, that

Let's also assume that Scord sources are located in `$HOME/scord`, that

dependencies were installed in `/opt`, and that we also want to install

`scord` in `/usr/local`. Taking into account all these requirements, `scord`

Scord in `/usr/local`. Taking into account all these requirements, Scord

can be built by running the following commands:

```bash

make

```

## Running tests

#### Running tests

Tests are integrated in [CTest](https://cmake.org/cmake/help/book/mastering-cmake/chapter/Testing%20With%20CMake%20and%20CTest.html), CMake's testing facility. Once built, the

tests can be run in parallel using the `ctest` command line tool:

Total Test time (real) =   0.14 sec

```

## Installing

#### Installing

Assuming that the CMAKE_INSTALL_PREFIX has been set (see previous step) and

that you have write permissions to the destination directory, `scord` can be

Assuming that the `CMAKE_INSTALL_PREFIX` has been set (see previous step) and

that you have write permissions to the destination directory, Scord can be

installed by running the following command from the build directory:

```bash

## Testing the configuration

If you just want to test that everything works as it should, you can start

`scord` in foreground mode and redirect its logging output to the console

Scord in foreground mode and redirect its logging output to the console

with the following command:

```bash

[2021-11-19 10:30:30.066151] [scord] [131119] [info]

[2021-11-19 10:30:30.066161] [scord] [131119] [info] [[ Start up successful, awaiting requests... ]]

```

Now we can use one of the example programs to send a `ping` RPC to `scord`:

Now we can use one of the example programs to send a `ping` RPC to Scord:

```bash