# Volume Shows Attached After Detach Operation Fails With Error " Unable to detach from guest transient domain

## Problem

* Volume unavailable inside the instance after failure to detach the volume from the instance with error as follows.

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{% tab title="None" %}

```none
DeviceDetachFailed: Device detach failed for vd[x]: Unable to detach from guest transient domain
```

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* Volume status is "attached" and "in-use" in Cinder DB.

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{% tab title="None" %}

```none
# openstack volume show volume_uuid --fit-width -c properties -c status+--------------------------------+--------------------------------------------------| Field | Value |+--------------------------------+--------------------------------------------------+| properties | attached_mode='rw' || status | in-use |+--------------------------------+---------------------------------------------------
```

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## Environment

* Platform9 Managed OpenStack - All Versions
* Cinder
* Nova
* Libvirt

## Cause

* The volume detach at the Libvirt driver level happens in two steps:
  * Detach from the persistent domain (affect instance upon next reboot).
  * Detach from the live domain (affect running instance) - Transient Domain.
* A detach from a live domain is a request from the host to the guest, which the guest can choose to ignore. If the guest has a file open on the volume by some process, it might ignore the request to detach that volume because the file is in use and logs below error in *ostackhost.log.*

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```none
TRACE oslo.service.loopingcall DeviceDetachFailed: Device detach failed for vd[x]: Unable to detach from guest transient domain.
```

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* If this scenario occurs, when a user retries to detach the volume, the volume is already detached from the persistent domain. Thus, it will fail the second attempt of detach operation with error:

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```none
ERROR nova.compute.manager [req-id  user-id] [instance: instance-id] Failed to detach volume volume_id from /dev/vd[x]
```

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* This is the expected behavior if the volume is detached from the persistent domain and unavailable inside the instance.

## Resolution

1. Restart of the instance is required to complete the detach operation.

## Additional Information

A patch to log the error observed while detaching the volume from a persistent domain was added in the upstream [OpenStack bugs launchpad #1633236](https://bugs.launchpad.net/nova/+bug/1633236).


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