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Document avoiding storage-level double replication - #387

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Document avoiding storage-level double replication#387
l4zy0n3 wants to merge 2 commits into
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l4zy0n3:longhorn-ha-storage-docs

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@l4zy0n3 l4zy0n3 commented Aug 20, 2026 •
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What

Document Longhorn single-replica, strict-local storage for SUSE Observability components that already replicate their data at the application layer. Also gives a backend-neutral recommendation to avoid redundant storage-level replication.

Verified behavior

  • Global/component precedence rendered against the shipped 2.10.3 chart.
  • Fresh PVCs receive their selected StorageClass; existing PVCs cannot change StorageClass (Kubernetes rejects the mutation), so migration is forward-only until claims are recreated.
  • Sizing render matrix: NonHA profiles do not qualify; Kafka, Elasticsearch, ZooKeeper and HDFS DataNode qualify in HA; ClickHouse qualifies only in 4000-ha; NameNode/SecondaryNameNode never qualify.
  • Global StorageClass blast radius inventoried: 18 PVC-producing resources in 150-ha, including metadata, backups, caches, VictoriaMetrics, vmagent and workload-observer.
  • Longhorn full-node drain behavior previously verified: default policy blocks on instance-manager PDB; always-allow completes. Documentation links to Longhorn's own node failure, graceful removal, and drain-policy guidance.

Documentation scope

  • Longhorn is detailed because it was tested live.
  • Other storage backends get the same general recommendation, deferring exact configuration/recovery to their documentation.
  • Explains global routing, mandatory HDFS metadata overrides, ClickHouse profile override, RWX incompatibility, immutable existing PVCs, and sequential node maintenance.

@l4zy0n3
l4zy0n3 requested a review from a team as a code owner August 20, 2026 10:31
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netlify Bot commented Aug 20, 2026 •
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@l4zy0n3
l4zy0n3 force-pushed the longhorn-ha-storage-docs branch from c6823e8 to b007ebf Compare August 20, 2026 10:41
@l4zy0n3 l4zy0n3 changed the title Document reducing storage overhead on replicated storage backends Document node-drain caveat for single-replica storage classes Aug 20, 2026
@l4zy0n3
l4zy0n3 force-pushed the longhorn-ha-storage-docs branch from b007ebf to d9eeb3a Compare August 20, 2026 10:46
@l4zy0n3 l4zy0n3 changed the title Document node-drain caveat for single-replica storage classes Document using Longhorn with self-replicating components Aug 20, 2026
@l4zy0n3
l4zy0n3 force-pushed the longhorn-ha-storage-docs branch 2 times, most recently from cfbcf45 to 1912e1e Compare August 20, 2026 10:53
@l4zy0n3
Document Longhorn single-replica storage guidance
90f7ad3 
Document how HA components with application-level replication can avoid
storage-level double replication. Include the Longhorn strict-local
StorageClass, global routing with HDFS metadata-node overrides, the
ClickHouse profile restriction, PVC immutability during upgrades, and
one-node-at-a-time maintenance guidance.
@l4zy0n3
l4zy0n3 force-pushed the longhorn-ha-storage-docs branch from 1912e1e to 90f7ad3 Compare August 26, 2026 10:05
@l4zy0n3 l4zy0n3 changed the title Document using Longhorn with self-replicating components Document avoiding storage-level double replication Aug 26, 2026
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@l4zy0n3
l4zy0n3 requested a review from rb3ckers October 28, 2026 08:54
@rb3ckers

rb3ckers commented Nov 9, 2026

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Superseded by #414

@rb3ckers rb3ckers closed this Nov 9, 2026
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@akashraj4261 akashraj4261 akashraj4261 approved these changes
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