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+# Configure a cluster
+
+*We use a command named `garagectl` which is in fact an alias you must define as explained in the [Control the daemon](./daemon.md) section.*
+
+In this section, we will inform garage of the disk space available on each node of the cluster
+as well as the site (think datacenter) of each machine.
+
+## Test cluster
+
+As this part is not relevant for a test cluster, you can use this three-liner to create a basic topology:
+
+```bash
+garagectl status | grep UNCONFIGURED | grep -Po '^[0-9a-f]+' | while read id; do 
+    garagectl node configure -d dc1 -c 1 $id
+done
+```
+
+## Real-world cluster
+
+For our example, we will suppose we have the following infrastructure (Capacity, Identifier and Datacenter are specific values to garage described in the following):
+
+| Location | Name    | Disk Space | `Capacity` | `Identifier` | `Zone` |
+|----------|---------|------------|------------|--------------|--------------|
+| Paris    | Mercury | 1 To       | `2`        | `8781c5`     | `par1`       |
+| Paris    | Venus   | 2 To       | `4`        | `2a638e`     | `par1`       |
+| London   | Earth   | 2 To       | `4`        | `68143d`     | `lon1`       |
+| Brussels | Mars    | 1.5 To     | `3`        | `212f75`     | `bru1`       |
+
+### Identifier
+
+After its first launch, garage generates a random and unique identifier for each nodes, such as:
+
+```
+8781c50c410a41b363167e9d49cc468b6b9e4449b6577b64f15a249a149bdcbc
+```
+
+Often a shorter form can be used, containing only the beginning of the identifier, like `8781c5`,
+which identifies the server "Mercury" located in "Paris" according to our previous table.
+
+The most simple way to match an identifier to a node is to run:
+
+```
+garagectl status
+```
+
+It will display the IP address associated with each node; from the IP address you will be able to recognize the node.
+
+### Zones
+
+Zones are simply a user-chosen identifier that identify a group of server that are grouped together logically.
+It is up to the system administrator deploying garage to identify what does "grouped together" means.
+
+In most cases, a zone will correspond to a geographical location (i.e. a datacenter).
+Behind the scene, Garage will use zone definition to try to store the same data on different zones,
+in order to provide high availability despite failure of a zone.
+
+### Capacity
+
+Garage reasons on an arbitrary metric about disk storage that is named the *capacity* of a node.
+The capacity configured in Garage must be proportional to the disk space dedicated to the node.
+Additionaly, the capacity values used in Garage should be as small as possible, with
+1 ideally representing the size of your smallest server.
+
+Here we chose that 1 unit of capacity = 0.5 To, so that we can express servers of size
+1 To and 2 To, as wel as the intermediate size 1.5 To.
+
+Note that the amount of data stored by Garage on each server may not be strictly proportional to
+its capacity value, as Garage will priorize having 3 copies of data in different zones,
+even if this means that capacities will not be strictly respected. For example in our above examples,
+nodes Earth and Mars will always store a copy of everything each, and the third copy will
+have 66% chance of being stored by Venus and 33% chance of being stored by Mercury.
+
+### Inject the topology
+
+Given the information above, we will configure our cluster as follow:
+
+```
+garagectl node configure -z par1 -c 2 -t mercury 8781c5
+garagectl node configure -z par1 -c 4 -t venus 2a638e
+garagectl node configure -z lon1 -c 4 -t earth 68143d
+garagectl node configure -z bru1 -c 3 -t mars 212f75
+```