Unable to Extend a Volume

Problem

  • Extending a volume results in error: "Failed to schedule_extend_volume: No valid backend was found."

  • The host does not have sufficient space for thin provisioning. The ratio of provisioned capacity over total capacity 1.47 has exceeded the maximum oversubscription ratio 1.00 on host

Environment

  • Platform9 Managed OpenStack - All Versions

Cause

  • Nova-Scheduler log shows "No valid backend was found" error.

851 13450 WARNING cinder.scheduler.filters.capacity_filter [req-12eb30d8-018e-450c-8bb4-e9e31b54edfa 062abbe158d84dd4a021aa0450a93bbb 0c3c9f76be7c4b08b86313c4f5b745e4 - default default] Insufficient free space for thin provisioning. The ratio of provisioned capacity over total capacity 1.57 has exceeded the maximum over subscription ratio 1.00 on host 166ae366-a3a3-4762-816b-b7c5bc073fdb@netapp_standard#10.81.85.20:/cinder01.889 13450 ERROR cinder.scheduler.manager [req-12eb30d8-018e-450c-8bb4-e9e31b54edfa 062abbe158d84dd4a021aa0450a93bbb 0c3c9f76be7c4b08b86313c4f5b745e4 - default default] Failed to schedule_extend_volume: No valid backend was found. Cannot place volume 02c2161f-8cb7-4ab9-ab15-b9981a73df6f on 166ae366-a3a3-4762-816b-b7c5bc073fdb@netapp_standard#10.81.85.20:/cinder03: NoValidBackend: No valid backend was found. Cannot place volume 02c2161f-8cb7-4ab9-ab15-b9981a73df6f on 166ae366-a3a3-4762-816b-b7c5bc073fdb@netapp_standard#10.81.85.20:/cinder03

  • On the host, we can see that the max_over_subscription_ratio is set to "1" in / opt/pf9/etc/pf9-cindervolume-base/conf.d.

[pf9@pdc-h-sdnp9os03 conf.d]$ grep max_over_subscription_ratio /opt/pf9/etc/pf9-cindervolume-base/conf.d/cinder_overrides.confmax_over_subscription_ratio = 1.0

Resolution

  1. The host does not have sufficient space to extend the volume. Add additional capacity to further extend the volume.

Additional Information

OpenStack documentation for more information relating to oversubscription for thinly-provisioned volumes.

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