github.com/ncodes/nomad@v0.5.7-0.20170403112158-97adf4a74fb3/website/source/guides/cluster/requirements.html.md (about)

     1  ---
     2  layout: "guides"
     3  page_title: "Nomad Client and Server Requirements"
     4  sidebar_current: "guides-cluster-requirements"
     5  description: |-
     6    Learn about Nomad client and server requirements such as memory and CPU
     7    recommendations, network topologies, and more.
     8  ---
     9  
    10  # Cluster Requirements
    11  
    12  ## Resources (RAM, CPU, etc.)
    13  
    14  **Nomad servers** may need to be run on large machine instances. We suggest
    15  having 8+ cores, 32 GB+ of memory, 80 GB+ of disk and significant network
    16  bandwidth. The core count and network recommendations are to ensure high
    17  throughput as Nomad heavily relies on network communication and as the Servers
    18  are managing all the nodes in the region and performing scheduling. The memory
    19  and disk requirements are due to the fact that Nomad stores all state in memory
    20  and will store two snapshots of this data onto disk. Thus disk should be at
    21  least 2 times the memory available to the server when deploying a high load
    22  cluster.
    23  
    24  **Nomad clients** support reserving resources on the node that should not be
    25  used by Nomad. This should be used to target a specific resource utilization per
    26  node and to reserve resources for applications running outside of Nomad's
    27  supervision such as Consul and the operating system itself.
    28  
    29  Please see the [reservation configuration](/docs/agent/configuration/client.html#reserved) for
    30  more detail.
    31  
    32  ## Network Topology
    33  
    34  **Nomad servers** are expected to have sub 10 millisecond network latencies
    35  between each other to ensure liveness and high throughput scheduling. Nomad
    36  servers can be spread across multiple datacenters if they have low latency
    37  connections between them to achieve high availability.
    38  
    39  For example, on AWS every region comprises of multiple zones which have very low
    40  latency links between them, so every zone can be modeled as a Nomad datacenter
    41  and every Zone can have a single Nomad server which could be connected to form a
    42  quorum and a region.
    43  
    44  Nomad servers uses Raft for state replication and Raft being highly consistent
    45  needs a quorum of servers to function, therefore we recommend running an odd
    46  number of Nomad servers in a region.  Usually running 3-5 servers in a region is
    47  recommended. The cluster can withstand a failure of one server in a cluster of
    48  three servers and two failures in a cluster of five servers. Adding more servers
    49  to the quorum adds more time to replicate state and hence throughput decreases
    50  so we don't recommend having more than seven servers in a region.
    51  
    52  **Nomad clients** do not have the same latency requirements as servers since they
    53  are not participating in Raft. Thus clients can have 100+ millisecond latency to
    54  their servers. This allows having a set of Nomad servers that service clients
    55  that can be spread geographically over a continent or even the world in the case
    56  of having a single "global" region and many datacenter.
    57  
    58  ## Ports Used
    59  
    60  Nomad requires 3 different ports to work properly on servers and 2 on clients,
    61  some on TCP, UDP, or both protocols. Below we document the requirements for each
    62  port.
    63  
    64  * HTTP API (Default 4646). This is used by clients and servers to serve the HTTP
    65    API. TCP only.
    66  
    67  * RPC (Default 4647). This is used by servers and clients to communicate amongst
    68    each other. TCP only.
    69  
    70  * Serf WAN (Default 4648). This is used by servers to gossip over the WAN to
    71    other servers. TCP and UDP.