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| layout | page_title | sidebar_current | description |
|---|---|---|---|
| docs | Nomad Client and Server Requirements | docs-cluster-requirements | Learn how to manually bootstrap a Nomad cluster using the server-join command. This section also discusses Nomad federation across multiple datacenters and regions. |
Cluster Requirements
Resources (RAM, CPU, etc.)
Nomad servers may need to be run on large machine instances. We suggest having 8+ cores, 32 GB+ of memory, 80 GB+ of disk and significant network bandwidth. The core count and network recommendations are to ensure high throughput as Nomad heavily relies on network communication and as the Servers are managing all the nodes in the region and performing scheduling. The memory and disk requirements are due to the fact that Nomad stores all state in memory and will store two snapshots of this data onto disk. Thus disk should be at least 2 times the memory available to the server when deploying a high load cluster.
Nomad clients support reserving resources on the node that should not be used by Nomad. This should be used to target a specific resource utilization per node and to reserve resources for applications running outside of Nomad's supervision such as Consul and the operating system itself.
Please see the reservation configuration for more detail.
Network Topology
Nomad servers are expected to have sub 10 millisecond network latencies between each other to ensure liveness and high throughput scheduling. Nomad servers can be spread across multiple datacenters if they have low latency connections between them to achieve high availability.
For example, on AWS every region comprises of multiple zones which have very low latency links between them, so every zone can be modeled as a Nomad datacenter and every Zone can have a single Nomad server which could be connected to form a quorum and a region.
Nomad servers uses Raft for state replication and Raft being highly consistent needs a quorum of servers to function, therefore we recommend running an odd number of Nomad servers in a region. Usually running 3-5 servers in a region is recommended. The cluster can withstand a failure of one server in a cluster of three servers and two failures in a cluster of five servers. Adding more servers to the quorum adds more time to replicate state and hence throughput decreases so we don't recommend having more than seven servers in a region.
Nomad clients do not have the same latency requirements as servers since they are not participating in Raft. Thus clients can have 100+ millisecond latency to their servers. This allows having a set of Nomad servers that service clients that can be spread geographically over a continent or even the world in the case of having a single "global" region and many datacenter.