First Experiment

Now that you have downloaded OpenDC, we will start creating a simple experiment. In this experiment we will compare the performance of a small, and a big data center on the same workload.

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Learning goal

During this tutorial, we will learn how to create and execute a simple experiment in OpenDC.

Designing a Data Center

The first requirement to run an experiment in OpenDC is a topology. A topology defines the hardware on which a workload is executed. Larger topologies will be capable of running more workloads, and will often quicker.

A topology is defined using a JSON file. A topology contains one or more clusters. clusters are groups of hosts on a specific location. Each cluster consists of one or more hosts. A host is a machine on which one or more tasks can be executed. hosts are composed of a cpu and a memory unit.

Simple Data Center

in this experiment, we are comparing two data centers. Below is an example of the small topology file:

{
    "clusters":
    [
        {
            "name": "C01",
            "hosts" :
            [
                {
                    "name": "H01",
                    "cpu":
                    {
                        "coreCount": 12,
                        "coreSpeed": 3300
                    },
                    "memory": {
                        "memorySize": 140457600000
                    }
                }
            ]
        }
    ]
}

This topology consist of a single cluster, with a single host.

tip

To use this topology in experiment copy the content to a new JSON file, or download it here

Simple Data Center

in this experiment, we are comparing two data centers. Below is an example of the bigger topology file:

{
    "clusters":
    [
        {
            "name": "C01",
            "hosts" :
            [
                {
                    "name": "H01",
                    "cpu":
                    {
                        "coreCount": 32,
                        "coreSpeed": 3200
                    },
                    "memory": {
                        "memorySize": 256000
                    }
                }
            ]
        },
        {
            "name": "C02",
            "hosts" :
            [
                {
                    "name": "H02",
                    "count": 6,
                    "cpu":
                    {
                        "coreCount": 8,
                        "coreSpeed": 2930
                    },
                    "memory": {
                        "memorySize": 64000
                    }
                }
            ]
        },
        {
            "name": "C03",
            "hosts" :
            [
                {
                    "name": "H03",
                    "count": 2,
                    "cpu":
                    {
                        "coreCount": 16,
                        "coreSpeed": 3200
                    },
                    "memory": {
                        "memorySize": 128000
                    }
                }
            ]
        }
    ]
}

Compared to the small topology, the big topology consist of three clusters, all consisting of a single host.

tip

To use this topology in experiment copy the content to a new JSON file, or download it here

info

For more in depth information about Topologies, see Topology

Workloads

Next to the topology, we need a workload to simulate on the data center. In OpenDC, workloads are defined as a bag of tasks. Each task is accompanied by one or more fragments. These fragments define the computational requirements of the task over time. For this experiment, we will use the bitbrains-small workload. This is a small workload of 50 tasks, spanning over a bit more than a month time. You can download the workload here

info

For more in depth information about Workloads, see Workload

Executing an experiment

To run an experiment, we need to create an experiment file. This is a JSON file, that defines what should be executed by OpenDC, and how. Below is an example of a simple experiment file:

{
    "name": "simple",
    "topologies": [{
        "pathToFile": "topologies/small.json"
    },
    {
        "pathToFile": "topologies/big.json"
    }],
    "workloads": [{
        "pathToFile": "traces/bitbrains-small",
        "type": "ComputeWorkload"
    }]
}

In this experiment, three things are defined. First, is the name. This defines how the experiment is called in the output folder. Second, is the topologies. This defines where OpenDC can find the topology files. Finally, the workloads. This defines which workload OpenDC should run. You can download the experiment file here

As you can see, topologies defines two topologies. In this case OpenDC will run two simulations, one with the small topology, and one with the big topology.

info

For more in depth information about Experiments, see Experiment

Running OpenDC

At this point, we should have all components to run an experiment. To make sure every file can be used by OpenDC, please create an experiment folder such as the one shown below:

── {simulation-folder-name} 📁 🔧
    ├── topologies 📁 🔒
    │   └── small.json 📄 🔧
    │   └── big.json 📄 🔧
    ├── experiments 📁 🔒
    │   └── simple_experiment.json 📄 🔧
    ├── workloads 📁 🔒
    │   └── bitbrains-small 📁 🔒
    │       └── fragments.parquet 📄 🔧
    │       └── tasks.parquet 📄 🔧
    ├── OpenDCExperimentRunner 📁 🔒
    │   └── lib 📁 🔒
    │   └── bin 📁 🔒
    ├── output 📁 🔒

Executing the experiment can be done directly from the terminal. Execute the following code from the terminal in simulation-folder-name

$ ./OpenDCExperimentRunner/bin/OpenDCExperimentRunner.sh --experiment-path "experiments/simple_experiment.json"