Elasticsearch Disk Watermark: Index Read-Only (FORBIDDEN/12)

How to fix it

Try these in order — the most common fix is first.

1. 1. Free disk first

   Copy steps
   1. Delete indices you no longer need, or delete and restore later from a snapshot
   2. Check usage with GET _cat/allocation
   Did this fix it? Yes No

2. 2. Temporarily raise the watermarks

   Copy steps
   1. PUT _cluster/settings with higher persistent values (Elastic's example: low 90%, high 95%, flood_stage 97%)
   2. This is a stopgap; reset by setting the same keys to null
   Did this fix it? Yes No

3. 3. Remove the read-only block

   Copy steps
   1. PUT <index>/_settings with index.blocks.read_only_allow_delete set to null
   2. Needed only if the block did not clear by itself
   Did this fix it? Yes No

4. 4. Fix the root cause

   Copy steps
   1. Add data nodes or disk, keep hardware matched within a tier
   2. Set ILM retention so old indices are deleted
   Did this fix it? Yes No

Symptoms

Indexing fails with 'index read-only / allow delete (api)' (FORBIDDEN/12); logs mention flood stage disk watermark exceeded; shards stop allocating at 85%.

Why it happens

• Data node disk above 95% used (defaults: low 85%, high 90%, flood stage 95%)
• Not enough nodes or disk for the data volume
• Old indices never deleted (no ILM retention)

This guide also covers

• elasticsearch index read only allow delete
• elasticsearch disk watermark exceeded
• elasticsearch flood stage disk watermark

The same problem in other apps

All plan limits, paywalls & watermarks guides →

• Algolia Record Quota Exceeded or Limit Reached (Algolia)

Other Elasticsearch errors

• Elasticsearch Cluster Health Yellow: Causes and Fixes
• Elasticsearch Cluster Health Red: How to Fix It
• Elasticsearch Unassigned Shards: Why and How to Fix
• Elasticsearch circuit_breaking_exception: Data Too Large
• Elasticsearch High JVM Memory Pressure and Out of Memory
• Elasticsearch Limit of Total Fields [1000] Exceeded
• Why Is Elasticsearch So Slow? Fixing Slow Searches
• Elasticsearch Cannot Change Field Mapping: Reindex Guide