Storage Monitoring

Storage monitoring covers disk health, capacity, I/O performance and the filesystems and distributed stores built on top of disks. This hub groups Netdata's ranked lists of monitoring tools for disk and NVMe health, ZFS and Ceph.

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Guides

Guides overview 1 page

Ceph Operations Guides

Practical guides for running, troubleshooting, and monitoring Ceph in production.

Cassandra Operations Guides 2 pages

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Cassandra disk space exhaustion: emergency recovery when the data volume fills

Emergency runbook for recovering a Cassandra node when disk space is exhausted, compaction stalls, and writes are rejected.

Cassandra Not enough space for compaction: STCS space amplification and recovery

Operational guide to diagnosing and recovering from Cassandra disk space exhaustion caused by STCS compaction space amplification, including per-strategy headroom and emergency remediation.

Ceph Operations Guides 20 pages

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Ceph backfill_toofull: recovery blocked because target OSDs are full

Diagnose and resolve Ceph backfill_toofull PGs where recovery stalls because target OSDs exceed the backfillfull ratio.

Ceph blocked ops: client I/O stuck behind a single slow OSD

Localize the single slow OSD blocking client writes, read the op pipeline stage, and decide disk vs network vs op queue.

Ceph BLUEFS_SPILLOVER: RocksDB metadata spilling onto the slow device

Diagnose and fix Ceph BLUEFS_SPILLOVER when BlueStore RocksDB metadata overflows the DB partition and tanks OSD commit latency.

Ceph capacity death spiral: an OSD fails and recovery has nowhere to go

An OSD fails on a hot cluster and backfill stalls because surviving OSDs are past the backfillfull ratio. Diagnose BACKFILL_TOOFULL and stalled recovery.

Ceph degraded objects: reduced redundancy and the race against a second failure

How to read ceph_num_objects_degraded correctly, distinguish it from misplaced objects, and alert on stalled recovery instead of normal healing.

Ceph FS_DEGRADED: standby MDS failed to take over a rank

Diagnose CephFS FS_DEGRADED when a standby MDS does not promote to a failed rank, and recover before the cluster escalates to MDS_ALL_DOWN.

Ceph HEALTH_ERR: reading the umbrella status and finding the real fault

How to interpret HEALTH_ERR as an umbrella status and drill into ceph health detail to find the specific child fault.

Ceph LARGE_OMAP_OBJECTS: the RGW bucket-index OMAP storm and resharding

Diagnose and fix Ceph LARGE_OMAP_OBJECTS warnings caused by oversized RGW bucket-index OMAP shards. Covers identification, dynamic and manual resharding, and prevention.

Ceph monitor quorum lost: the cluster can no longer update its maps

Diagnose and recover a Ceph cluster that has lost monitor quorum and can no longer commit map updates.

Ceph monitoring checklist: the signals every production cluster needs

Operational reference covering the Prometheus metrics and health checks every production Ceph cluster needs, organized by monitoring maturity level.

Ceph nearfull: the 85% warning that decides whether the cluster can heal

Why OSD_NEARFULL is a recovery-headroom warning, not a cosmetic one, and how to keep one OSD failure from deadlocking self-healing.

Ceph OSD down: telling a dead disk apart from a network blip

Triage a Ceph OSD marked down by separating disk failure from network loss, OOM-kill, and daemon crashes before recovery starts.

Ceph OSD flapping: OSDs cycling up and down and the peering storm that follows

Diagnose and stabilize Ceph OSD flapping before the peering storm cascades into a cluster-wide outage.

Ceph OSD_FULL: all writes stopped at the 95% full ratio

Diagnose and recover from a Ceph OSD_FULL condition where all writes stop at the 95% full ratio, and prevent it from recurring.

Ceph PG degraded: fewer replicas than the pool size, and when it matters

What a degraded Ceph placement group means, when it is normal during recovery, and how to alert on it without flooding tickets.

Ceph PG down: no surviving replica for reads or writes

Diagnose and recover Ceph placement groups stuck in the down state, where no surviving replica can serve reads or writes.

Ceph PG incomplete: placement groups that cannot serve I/O

What a Ceph PG in incomplete state means, how to diagnose peering failures with ceph pg query, and the recovery paths from OSD restart to force-create-pg.

Ceph PG inconsistent (OSD_SCRUB_ERRORS): scrub found replica divergence

Ceph scrub found replica divergence. Diagnose which copy is corrupt before running ceph pg repair, or you may propagate the corruption.

Ceph slow requests (SLOW_OPS): operations blocked past osd_op_complaint_time

Diagnose and resolve Ceph SLOW_OPS warnings where operations exceed osd_op_complaint_time (default 30s) and stall in the OSD pipeline.

Ceph unfound objects: the cluster cannot locate a surviving copy

Diagnosing and resolving Ceph unfound objects when all replicas or EC chunks are on down or destroyed OSDs.

ClickHouse Operations Guides 3 pages

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ClickHouse disk space collapse: why merges need free space and how the spiral starts

Why ClickHouse background merges need temporary disk headroom and how crossing the 85-90% threshold triggers a self-reinforcing spiral of stalled merges, accumulating parts, and accelerating consumption.

ClickHouse disk space monitoring: free_space, unreserved_space, and the 80% target

Understand ClickHouse disk space as an operational dependency, not just capacity. Interpret system.disks metrics, maintain merge headroom, and avoid the disk space death spiral.

ClickHouse merge death spiral: when parts accumulate faster than merges consolidate

Break the feedback loop where ClickHouse inserts outrun background merges, parts pile up, and writes are delayed or rejected.

CockroachDB Operations Guides 2 pages

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CockroachDB changefeed lag: changefeed_max_behind_nanos and the GC time bomb

Diagnose and fix CockroachDB changefeed lag before protected timestamps block MVCC garbage collection and fill your disk.

CockroachDB LSM compaction death spiral: L0 sublevels, read amplification, and write stalls

Diagnose and break the LSM compaction death spiral in CockroachDB by monitoring L0 sublevels, read amplification, and write stalls before nodes lose leases.

Docker Operations Guides 3 pages

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Docker disk space full: how to troubleshoot /var/lib/docker

Diagnose and resolve Docker disk exhaustion on /var/lib/docker by identifying dominant space consumers across images, containers, volumes, build cache, and logs.

Docker image cleanup: safe pruning strategies for production hosts

Safe commands and filters to reclaim Docker disk space without stopping running containers or deleting data you still need.

Docker volume cleanup: finding and removing orphaned volumes

Find and safely remove orphaned Docker volumes that waste disk space and complicate operations.

Elasticsearch Operations Guides 3 pages

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Elasticsearch disk watermark cascade: from low watermark to cluster-wide read-only

Operational guide to diagnosing and recovering from the Elasticsearch disk watermark cascade: low, high, and flood stage thresholds, read-only index blocks, and relocation storms.

Elasticsearch FORBIDDEN/12/index read-only / allow delete (api) — flood stage recovery

Recover from Elasticsearch cluster_block_exception when flood-stage disk watermark sets index.blocks.read_only_allow_delete, blocking writes.

Elasticsearch high disk watermark [90%] exceeded: shard relocation and the cascade

Diagnose and stop the Elasticsearch disk watermark cascade when shard relocations from high-watermark nodes push targets toward their own limits.

Kubernetes Operations Guides 4 pages

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Kubernetes Monitoring Checklist: The Signals Every Production Cluster Needs

A structured checklist of production signals across the Kubernetes control plane, nodes, workloads, networking, DNS, storage, and security.

Kubernetes node DiskPressure: detection, eviction, and recovery

Detect disk pressure on Kubernetes nodes before evictions start. Understand nodefs, imagefs, inode exhaustion, and recovery steps for production clusters.

Kubernetes pod stuck on volume mount: CSI, permissions, and timeouts

Diagnose and fix pods stuck during volume mount operations caused by CSI driver failures, permission mismatches, and mount timeouts.

Kubernetes PVC stuck Pending: storage class, provisioner, and quota

Diagnose and fix PersistentVolumeClaims stuck in Pending due to StorageClass, provisioner, or quota issues.

Microsoft SQL Server Operations Guides 3 pages

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SQL Server Error 823 and 824: I/O and logical consistency errors

Triage SQL Server severity-24 I/O errors: hard OS-level failures (823), logical consistency and checksum errors (824), and the 825 read-retry canary, plus DBCC CHECKDB, suspect_pages, and restore-first response.

SQL Server Error 825: read-retry succeeded and the disk is failing

SQL Server Error 825 means a disk read eventually succeeded after retries, but the storage medium is deteriorating and a hard 823/824 is coming.

SQL Server PAGEIOLATCH waits: the buffer pool waiting on slow storage

Diagnose PAGEIOLATCH_SH and PAGEIOLATCH_EX by separating memory pressure from slow storage, using sys.dm_io_virtual_file_stats and wait stats deltas.

MongoDB Operations Guides 4 pages

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MongoDB checkpoint duration climbing: diagnosing slow WiredTiger checkpoints

Diagnose and fix climbing WiredTiger checkpoint duration before it exceeds the 60-second interval and freezes writes.

MongoDB checkpoint stall write freeze: when all writes stop with no error

Troubleshoot the WiredTiger checkpoint stall that silently blocks all MongoDB writes with no errors, leaving reads partially functional.

MongoDB disk full: emergency recovery when mongod can't write the journal

Emergency triage and recovery steps when MongoDB exhausts disk space and the journal cannot write, including WiredTiger space reclamation and recovery procedures.

MongoDB journal sync latency high: the storage signal that warns 60 seconds early

Detect, diagnose, and fix high WiredTiger journal sync latency in MongoDB before it stalls j:true and w:majority writes.

Redis Operations Guides 1 page

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Redis aof_last_write_status:err: AOF write failures and recovery

Diagnose and recover when Redis AOF writes fail, including disk full, I/O errors, and the path from aof_last_write_status:err back to ok.

VMware vSphere Operations Guides 5 pages

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vCenter /storage/db full: vPostgres stops and the whole management plane dies

When the VCSA /storage/db partition fills, vPostgres cannot write WAL, crashes, and vpxd loses its database. Diagnose the cliff-edge failure and recover safely.

vCenter /storage/log full: the log-bomb disk death spiral

Diagnose and stop a vCenter /storage/log log bomb before it takes down vpxd and the management plane.

vSphere 'Virtual machine disks consolidation is needed': clearing the warning without stunning the VM

How to clear vSphere's 'Virtual machine disks consolidation is needed' warning safely, including lock conflicts, free space requirements, and stun-free consolidation windows.

vSphere datastore full: 'No space left on device', paused VMs, and power-on failures

Recover from a full vSphere datastore: diagnose paused VMs, .vswp power-on failures, and 'No space left on device' errors, and find the snapshot or thin VMDK consuming the space.

vSphere datastore latency high: reading GAVG, DAVG, and KAVG

How to read vSphere's GAVG, DAVG, and KAVG counters to localize high datastore latency to the array, the VMkernel, or both.

Apache ZooKeeper Operations Guides 1 page

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ZooKeeper autopurge not configured: snapshots and logs filling the disk over months

Diagnose and fix ZooKeeper disk exhaustion caused by disabled autopurge, with safe checks for snapshot and transaction log accumulation.

Academy

Analyze & Reduce Disk I/O Bottlenecks: Top Techniques

Mastering Disk Performance for Optimal System Health

Adaptec RAID Monitoring

Learn everything about monitoring & troubleshooting Adaptec RAID, what metrics are important to monitor and why, and how to monitor Adaptec RAID with Netdata.

Ceph Monitoring

Learn everything about monitoring & troubleshooting Ceph, what metrics are important to monitor and why, and how to monitor Ceph with Netdata.

Dell EMC ScaleIO Monitoring

Learn everything about monitoring & troubleshooting Dell EMC ScaleIO, what metrics are important to monitor and why, and how to monitor ScaleIO with Netdata.

DMCache Monitoring

Learn everything about monitoring & troubleshooting DMCache, what metrics are important to monitor and why, and how to monitor DMCache with Netdata.

EOS Monitoring

Learn everything about monitoring & troubleshooting EOS, what metrics are important to monitor and why, and how to monitor EOS with Netdata.

FreeBSD NFS Monitoring

Learn everything about monitoring & troubleshooting FreeBSD NFS, what metrics are important to monitor and why, and how to monitor FreeBSD NFS with Netdata.

Generic storage enclosure tool Monitoring

Learn everything about monitoring & troubleshooting Generic storage enclosure tool, what metrics are important to monitor and why, and how to monitor Generic storage enclosure tool with Netdata.

Hadoop Distributed File System (HDFS) Monitoring

Learn everything about monitoring & troubleshooting Hadoop Distributed File System (HDFS), what metrics are important to monitor and why, and how to monitor HDFS with Netdata.

HDD Temperature Monitoring

Learn everything about monitoring & troubleshooting HDD temperature, what metrics are important to monitor and why, and how to monitor HDD temperature with Netdata.

HPE Smart Arrays Monitoring

Learn everything about monitoring & troubleshooting HPE Smart Arrays, what metrics are important to monitor and why, and how to monitor HPE Smart Arrays with Netdata.

IBM Spectrum Monitoring

Learn everything about monitoring & troubleshooting IBM Spectrum, what metrics are important to monitor and why, and how to monitor IBM Spectrum with Netdata.

IBM Spectrum Virtualize Monitoring

Learn everything about monitoring & troubleshooting IBM Spectrum Virtualize, what metrics are important to monitor and why, and how to monitor IBM Spectrum Virtualize with Netdata.

IPFS Monitoring

Learn everything about monitoring & troubleshooting IPFS, what metrics are important to monitor and why, and how to monitor IPFS with Netdata.

Lustre Metadata Monitoring

Learn everything about monitoring & troubleshooting Lustre metadata, what metrics are important to monitor and why, and how to monitor Lustre metadata with Netdata.

LVM logical volumes Monitoring

Learn everything about monitoring & troubleshooting LVM logical volumes, what metrics are important to monitor and why, and how to monitor LVM logical volumes with Netdata.

MegaCLI MegaRAID Monitoring

Learn everything about monitoring & troubleshooting MegaCLI MegaRAID, what metrics are important to monitor and why, and how to monitor MegaCLI MegaRAID with Netdata.

MogileFS Monitoring

Learn everything about monitoring & troubleshooting MogileFS, what metrics are important to monitor and why, and how to monitor MogileFS with Netdata.

NetApp ONTAP API Monitoring

Learn everything about monitoring & troubleshooting NetApp ONTAP API, what metrics are important to monitor and why, and how to monitor NetApp ONTAP API with Netdata.

NetApp Solidfire Monitoring

Learn everything about monitoring & troubleshooting NetApp Solidfire, what metrics are important to monitor and why, and how to monitor NetApp Solidfire with Netdata.

Nextcloud Monitoring

Learn everything about monitoring & troubleshooting Nextcloud, what metrics are important to monitor and why, and how to monitor Nextcloud with Netdata.

NVMe Monitoring

Learn everything about monitoring & troubleshooting NVMe, what metrics are important to monitor and why, and how to monitor NVMe with Netdata.

S.M.A.R.T. attributes Monitoring

Learn about monitoring & troubleshooting S.M.A.R.T. attributes, what metrics are important and why, and how to monitor S.M.A.R.T. attributes with Netdata.

S.M.A.R.T. Monitoring

Learn everything about monitoring & troubleshooting S.M.A.R.T., what metrics are important to monitor and why, and how to monitor S.M.A.R.T. with Netdata.

Samba Monitoring

Learn everything about monitoring & troubleshooting Samba, what metrics are important to monitor and why, and how to monitor Samba with Netdata.

StoreCLI RAID Monitoring

Learn everything about monitoring & troubleshooting StoreCLI RAID, what metrics are important to monitor and why, and how to monitor StoreCLI RAID with Netdata.

Storidge Monitoring

Learn everything about monitoring & troubleshooting Storidge, what metrics are important to monitor and why, and how to monitor Storidge with Netdata.

Synology ActiveBackup Monitoring

Learn everything about monitoring & troubleshooting Synology ActiveBackup, what metrics are important to monitor and why, and how to monitor Synology ActiveBackup with Netdata.

ZFS Pools Monitoring

Learn everything about monitoring & troubleshooting ZFS Pools, what metrics are important to monitor and why, and how to monitor ZFS Pools with Netdata.

Case Studies

Streamlining VM Monitoring with Netdata

Achieving Operational Efficiency in Rapidly Changing Environments

Enhancing Digital Media Excellence with Netdata

SHED's Story of Optimizing Network Performance.

Resources

10 Best Disk Health & S.M.A.R.T. Monitoring Tools

The 10 best disk health and S.M.A.R.T. monitoring tools, ranked on attribute depth, failure alerting, real-time resolution, fleet scale, and cost.

Best Ceph Monitoring Tools: 7 Options Ranked (2026)

We ranked 7 Ceph monitoring tools on metric depth, time to value, alerting, and fleet visibility. See where Netdata, Prometheus, Grafana, and Zabbix land.

Best LVM & Linux Storage Monitoring Tools (9 Ranked)

The 9 best LVM monitoring tools for Linux, ranked by thin pool depth, collection speed, and alerting. See which tools actually see past the filesystem layer.

Best NVMe & SSD Health Monitoring Tools: 9 Options Ranked

We ranked 9 NVMe and SSD health monitoring tools on SMART attribute depth, fleet coverage, alerting, and cost. See where Netdata, Zabbix, and Prometheus land.

Best ZFS Monitoring Tools: 7 Ranked (August 2026)

We ranked the 7 best ZFS monitoring tools on pool health, ARC stats, scrub tracking, and alerting. See how Netdata, Prometheus, Zabbix, and Checkmk compare.

Blog

Native macOS Monitoring: Logs, Sensors, GPU & Hardware Health

Unified logs, power and sensors, Apple-silicon GPU, per-app metrics, storage health, and network topology — read through Apple's own frameworks, at per-second resolution.

Monitoring Disks: Workload, Latency & Saturation

Proactive Strategies for Disk Health and Performance

How to monitor the disk usage on your infrastructure

Techniques for Managing Storage Efficiently and Avoiding Outages

How To Monitor Disks & Filesystems With eBPF

Preventing Disk Space Issues with Proactive Monitoring