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Object Storage Daemons (OSDs) are the core storage components of a Ceph cluster. Each OSD manages a physical disk and handles data replication, recovery, and rebalancing. This page allows you to view OSD status, add new OSDs, and safely remove existing ones.

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Key Concepts

OSD

Object Storage Daemon - a service that stores data on a physical disk and handles replication.

Device Class

The type of storage device: HDD (rotational), SSD (solid-state), or NVMe (high-speed SSD).

Up/Down

Whether the OSD process is running (Up) or stopped (Down).

In/Out

Whether the OSD is participating in data placement (In) or excluded from it (Out).

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Required Permissions

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OSD Status

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Up/Down Status

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In/Out Status

An OSD can be Up but Out - this means it’s running but not receiving new data. This is commonly used during maintenance or before removal.

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Device Classes

Device classes are used by CRUSH rules to place data on specific storage types. For example, you can configure pools to use only SSDs for high-performance workloads.

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How to View OSDs

1

Select Cluster

Choose a Ceph cluster from the cluster dropdown. The first ready cluster is selected by default.
2

View OSD List

The table shows all OSDs with their status, host, device class, placement groups, and utilization.
3

Filter and Search

Use the search box to find OSDs by ID, hostname, or device class. Filter by status (Up, Down, In, Out).
4

Review Statistics

Check the summary cards for:
  • Total OSDs: All OSDs in the cluster
  • Up: Running OSD daemons
  • Down: Stopped or unresponsive OSDs
  • In Cluster: OSDs actively storing data
  • Total Capacity: Combined storage across all OSDs
  • Avg Usage: Average utilization percentage

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How to Add an OSD

Adding an OSD creates a new storage daemon on an available disk.
1

Click Add OSD

Click the Add OSD button in the page header.
2

View Available Disks

A drawer opens showing all available (unused) disks across cluster nodes.
3

Select Disks

Check the disks you want to use as OSDs. Each disk shows:
  • Device path (e.g., /dev/sdb)
  • Host where the disk is located
  • Disk size
  • Device type (HDD, SSD, NVMe)
4

Add OSDs

Click Add OSDs to create OSD daemons on the selected disks.
5

Monitor Progress

The operation runs in the background. The new OSDs will appear in the list once created.
Only available disks that don’t already have OSDs are shown. If no disks appear, all disks may already be in use or there may be no OSD-role nodes in the cluster.

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How to Mark an OSD Out

Marking an OSD “out” removes it from data placement, causing data to migrate to other OSDs.
1

Find the OSD

Locate the OSD in the list.
2

Open Actions Menu

Click the actions menu (dropdown arrow) on the OSD row.
3

Click Mark Out

Select Mark Out from the menu.
4

Wait for Migration

Data will begin migrating to other OSDs. Monitor cluster health until all placement groups are active+clean.
Mark Out is the first step in safely removing an OSD. It triggers data migration without stopping the OSD daemon.

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How to Mark an OSD In

Marking an OSD “in” adds it back to data placement.
1

Find the OSD

Locate the OSD that is currently marked out.
2

Open Actions Menu

Click the actions menu on the OSD row.
3

Click Mark In

Select Mark In from the menu.
4

Wait for Rebalancing

Data will begin distributing to this OSD. The cluster will rebalance automatically.

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How to Scrub an OSD

Scrubbing verifies data integrity by comparing object replicas across OSDs.
1

Find the OSD

Locate the OSD to scrub.
2

Open Actions Menu

Click the actions menu on the OSD row.
3

Select Scrub Type

Choose either:
  • Scrub: Light verification of object metadata
  • Deep Scrub: Full verification including data checksums
4

Monitor Progress

The scrub runs in the background. Check cluster logs for results.
Deep scrub is I/O intensive and may impact performance. Schedule deep scrubs during low-usage periods.

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How to Remove an OSD

Removing an OSD is a multi-step process to ensure data safety. A guided wizard walks you through the process.
1

Select OSD(s)

Select one or more OSDs using checkboxes, or click Remove OSD from the actions menu.
2

Click Remove

Click the Remove button to open the removal wizard.
3

Pre-flight Check

Review the selected OSDs and the amount of data that will need to migrate.
4

Safety Check

The system checks if removal is safe:
  • Safe to Destroy: All data has sufficient replicas elsewhere
  • Not Safe: Removal would cause data loss (requires force removal)
5

Data Migration

Click Start Migration to mark OSDs out and begin data migration. Wait for all placement groups to reach active+clean state.
6

Confirm Removal

Type REMOVE to confirm you want to permanently remove the OSDs.
7

Cleanup Commands

After removal, the wizard provides ceph orch device zap commands to clean the disks for reuse.
DESTRUCTIVE OPERATION: Removing an OSD is permanent. Ensure data migration is complete before confirming removal. Skipping migration may cause data loss.

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OSD Table Fields

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Removal Wizard Steps

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Step 1: Pre-flight Check

Shows selected OSDs with:
  • OSD ID and hostname
  • Device class
  • Data to migrate
  • Placement group count

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Step 2: Safety Check

Verifies if OSDs can be safely destroyed:
  • Checks replica counts for all affected placement groups
  • Shows “Safe to Destroy” or “Not Safe to Destroy”
  • Option to force removal if unsafe (not recommended)

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Step 3: Data Migration

  • Marks OSDs as “out”
  • Monitors data migration progress
  • Shows when all placement groups are active+clean
  • Option to skip waiting (may cause data loss)

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Step 4: Confirm Removal

  • Requires typing REMOVE to confirm
  • Option to force removal (skips safety checks)
  • Executes OSD deletion

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Step 5: Cleanup

  • Shows completion status
  • Provides zap commands for disk cleanup
  • Commands can be copied to clipboard

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Troubleshooting

  • Check if the OSD host is accessible
  • Verify the OSD daemon is running: systemctl status ceph-osd@<id>
  • Check for disk failures or hardware issues
  • Review OSD logs for errors
  • All disks may already have OSDs
  • Ensure the node has the OSD role assigned
  • Check if disks are properly detected by the system
  • Verify disks aren’t mounted or in use by other services
  • Consider adding more OSDs to the cluster
  • Check if other OSDs are down or out
  • Verify CRUSH rules are distributing data evenly
  • Consider reweighting OSDs to balance load
  • This is normal for large amounts of data
  • Check network bandwidth between nodes
  • Verify no backfill/recovery throttling is set too low
  • Monitor ceph status for recovery progress
  • Some placement groups don’t have enough replicas
  • Wait for recovery to complete
  • Check if other OSDs are down
  • Use force removal only if you accept potential data loss
  • Check cluster health for blocking issues
  • Verify network connectivity
  • Check if the OSD daemon is still running
  • Review operation logs for specific errors
  • Deep scrub is I/O intensive on large OSDs
  • Check OSD performance and disk health
  • Consider adjusting scrub scheduling options
  • Large OSDs with many objects take longer

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FAQ

Up/Down indicates whether the OSD daemon process is running.In/Out indicates whether the OSD participates in data placement.An OSD can be:
  • Up + In: Normal operation, storing and serving data
  • Up + Out: Running but not receiving data (draining)
  • Down + In: Not running but expected to return (temporary failure)
  • Down + Out: Not running and excluded from placement
Mark Out when:
  • Performing temporary maintenance
  • The OSD will return to service
  • You want to drain data without removing the OSD
Remove when:
  • Decommissioning a disk permanently
  • Replacing failed hardware
  • The OSD will not return to service
When you add an OSD:
  1. The Ceph orchestrator deploys an OSD daemon on the disk
  2. The OSD is added to the CRUSH map
  3. The cluster begins rebalancing data to include the new OSD
  4. Data gradually distributes across all OSDs
Removal time depends on:
  • Amount of data on the OSD
  • Network speed between nodes
  • Number of remaining OSDs
  • Current cluster load
Small OSDs may complete in minutes; large OSDs can take hours.
This check verifies that removing the OSD won’t cause data loss:
  • Checks all placement groups on the OSD
  • Ensures each PG has sufficient replicas on other OSDs
  • If any PG would lose its last copy, removal is blocked
Force removal bypasses this check but may cause data loss.
After removing an OSD, the disk may still have Ceph metadata. The ceph orch device zap command:
  • Removes all Ceph data from the disk
  • Clears partition tables and LVM data
  • Makes the disk available for reuse
This is optional but recommended before reusing the disk.
Avoid force removal unless you:
  • Understand the risk of data loss
  • Have backups of critical data
  • Are removing already-failed OSDs
  • Accept that some data may be lost
Normal removal with data migration is always safer.
Reweight adjusts how much data an OSD receives (0.0 to 1.0):
  • 1.0: Full weight, normal data distribution
  • 0.5: Half weight, receives half the normal data
  • 0.0: No data (equivalent to marking out)
Use reweight to gradually drain an OSD or balance uneven utilization.
Deep scrub verifies data integrity at the bit level:
  • Run periodically for data verification
  • After suspected disk issues
  • When data corruption is suspected
Deep scrubs are scheduled automatically but can be run manually.