Device Management

Ceph tracks which hardware storage devices (e.g., HDDs, SSDs) are consumed by which daemons, and collects health metrics about those devices in order to provide tools to predict and/or automatically respond to hardware failure.

Device tracking

You can query which storage devices are in use with:

ceph device ls

You can also list devices by daemon or by host:

ceph device ls-by-daemon <daemon>
ceph device ls-by-host <host>

For any individual device, you can query information about its location and how it is being consumed with:

ceph device info <devid>

Enabling monitoring

Ceph can also monitor health metrics associated with your device. For example, SATA hard disks implement a standard called SMART that provides a wide range of internal metrics about the device’s usage and health, like the number of hours powered on, number of power cycles, or unrecoverable read errors. Other device types like SAS and NVMe implement a similar set of metrics (via slightly different standards). All of these can be collected by Ceph via the smartctl tool.

You can enable or disable health monitoring with:

ceph device monitoring on


ceph device monitoring off


If monitoring is enabled, metrics will automatically be scraped at regular intervals. That interval can be configured with:

ceph config set mgr mgr/devicehealth/scrape_frequency <seconds>

The default is to scrape once every 24 hours.

You can manually trigger a scrape of all devices with:

ceph device scrape-health-metrics

A single device can be scraped with:

ceph device scrape-health-metrics <device-id>

Or a single daemon’s devices can be scraped with:

ceph device scrape-daemon-health-metrics <who>

The stored health metrics for a device can be retrieved (optionally for a specific timestamp) with:

ceph device get-health-metrics <devid> [sample-timestamp]

Failure prediction


Health alerts

The mgr/devicehealth/warn_threshold controls how soon an expected device failure must be before we generate a health warning.

The stored life expectancy of all devices can be checked, and any appropriate health alerts generated, with:

ceph device check-health

Automatic Mitigation

If the mgr/devicehealth/self_heal option is enabled (it is by default), then for devices that are expected to fail soon the module will automatically migrate data away from them by marking the devices “out”.

The mgr/devicehealth/mark_out_threshold controls how soon an expected device failure must be before we automatically mark an osd “out”.