Source:Troubleshooting Citrix XEN Server

Citrix XenServer

Error when using quiesced snapshots

Problem

Using VM.snapshot_with_quiesce method fails in Citrix Hypervisor ≥ 8.1 or in the version ≥ 9.0.x.x drivers.

Cause

VSS and quiesced snapshots of Windows VMs capability have been removed in Citrix Hypervisor ≥ 8.1 and in the version ≥ 9.0.x.x drivers. They are only supported in Citrix Hypervisor ≤ 8.0.

⇒ Solution

If you want to continue using the quiesced snapshot feature with Windows VMs hosted on Citrix Hypervisor 8.0 and earlier, do not update to the 9.0.x.x drivers.

CBT backup fails because Hypervisor TLS certificate contains wrong IP address

Problem

CBT backup fails with the NBD client connection error:

Failed to get NBD client for device '******: NBD client connection error: hostname '****' doesn't match u'******

Cause

The TLS certificate of a Xen Server contains the wrong IP address. Therefore no NBD session can be established.

⇒ Solution

Check all Citrix Hypervisors in the Pool whether the IP address in the certificate matches.
On the Citrix Hypervisor where it does not match, execute the following commands:

Create a backup of the existing certificate by using

mv /etc/xensource/xapi-ssl.pem /etc/xensource/xapi-ssl.pem.$(date -u +%Y%m%d)

Create a new certificate

/opt/xensource/libexec/generate_ssl_cert /etc/xensource/xapi-ssl.pem <ip-address or FQDN>

Restart XenAPI service

systemctl restart xapi

Restart NBD Service

systemctl restart xapi-nbd

Message "Upload to URL ... failed" appears during restore, "insufficient space" error occurs during backup

Problems

Restore fails with an error:

"Upload to URL ... failed."

SR_BACKEND_FAILURE_44: : There is insufficient space to create snapshot on Storage Repository.

Possible cause

There is not enough space available on the default storage.
If the "insufficient space" error occurs during the backup, it might be related to the snapshot process. XenServer was unable to create a snapshot for the VM because there was not enough space in your Storage Repository.

⇒ Solution

Use XenCenter to select another default storage that has enough free disk capacity to store the virtual disk(s).

Other issues

Some errors are not reported in detail by XEN API. More information can be found in XenServer in /var/log directory.
In some pool configurations all pool members must have their management interface listed in DNS.
If the settings below don't agree on asynchronous routing and connection drops and/or 3 second or 80 second delays, opening sockets may occour. This is very similar to having 2 network cards configured with ipv4 to the same subnet and connected to the same switch.
Most network related performance and reliability issues can be resolved with Troubleshoot networking (XenServer).
In some situations when using thin storage repositories, an sr rescan is necessary to re-detect free space before a backup or restore.

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