diff --git a/CHANGES.rst b/CHANGES.rst index 1a0e08c..24b3231 100644 --- a/CHANGES.rst +++ b/CHANGES.rst @@ -6,6 +6,7 @@ Changes Unreleased ========== +- Document dedicated master nodes on the Services page - Consolidate ``cloud-reference``, ``cloud-howtos``, and ``cloud-tutorials`` - Adjust links to accompany renaming to ``cloud-docs`` - Adjust intersphinx references to accompany consolidation into single repository diff --git a/docs/reference/services.md b/docs/reference/services.md index a605e72..9a066b4 100644 --- a/docs/reference/services.md +++ b/docs/reference/services.md @@ -50,7 +50,7 @@ _large production workloads_ - Any cluster size - Custom compute options -- Dedicated master nodes +- {ref}`Dedicated master nodes ` - Unlimited Storage - Custom Backups - Premium Support @@ -154,6 +154,47 @@ three (e.g., 3, 6, 9, 12, etc.) provides optimal distribution across zones, it is not strictly required for high availability. +(dedicated-master-nodes)= +## Dedicated master nodes + +By default, every node in a cluster is master-eligible: on top of storing and +querying data, any node can be elected to manage the cluster state—keeping +track of which nodes are members, where shards live, and coordinating changes +to that metadata. On smaller clusters this shared arrangement works fine. On +large or busy clusters it can work against you, because the elected master +competes for CPU and memory with the same query and ingest traffic it is meant +to coordinate—the data node under the most load is also the one holding the +cluster together. + +Dedicated master nodes split those two jobs apart. The cluster runs a small, +separate pool of nodes that only manage the cluster state; they hold no data +and answer no queries, so coordination stays responsive no matter how hard the +data nodes are working. In practice this means steadier cluster management and +cleaner failover on larger deployments. + +**When to use them**
+Consider dedicated master nodes once a cluster grows past a handful of data +nodes, sustains heavy ingest or query load, or has strict availability +requirements. Smaller clusters don't need them—the data nodes take on the +master role without any trouble. + +**How they work**
+- You opt into dedicated master nodes when deploying a cluster. They are + available on the larger dedicated sizes (CR3 and up). +- The pool always runs an odd number of nodes—three by default, optionally + five—so a master can always be elected by a majority (quorum). An even number + adds cost without improving fault tolerance, so it isn't offered. +- Master nodes are distributed across availability zones like data nodes, and + each is deployed with its own storage. Their size and count are set when the + cluster is created and stay fixed when you scale the data nodes up or down. + +**Billing**
+Dedicated masters are billed as additional nodes: compute for each master while +the cluster is running, plus their storage. Suspending a cluster pauses master +compute along with the data nodes; master storage keeps being billed, the same +way data storage does. See {ref}`billing ` for details. + + ## Custom For organizations with specialized requirements that go beyond the Shared and