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I have a backup failure showing error:

 Failed to open VDDK disk [[vsanDatastore] be123456677777777/vm1vmdk] ( is read-only mode - [true] )
Logon attempt with parameters [VC/ESX: [dc1.nm.org];Port: 443;Login: [;VMX Spec: [moref=vm-1104];Snapshot mor: [snapshot-253990;Transports: [nbd];Read Only: [true]] failed because of the following errors:
Failed to open disk for read.
Failed to upload disk 'vddkConnSpec>'
Agent failed to process method {DataTransfer.SyncDisk}.

 

It was working only when selecting nbdssl transport mode . i know it is using network over ssl .Can someone advise why it is working only nbdssl and what is it doing in the background?

Is the VM encrypted by chance?   If so you need that turned on - https://helpcenter.veeam.com/docs/backup/vsphere/encrypted_vms_backup.html?ver=120#:~:text=If%20you%20want%20to%20use%20NBDSSL,%20select%20the%20Enable%20host

 

@Nikks -

Can you take a snapshot directly on the VM within your hypervsor? It looks like Veeam is having a problem doing that task? What other transport mode are you attempting? Are you saying it does work with nbdssl and nothing else? (hotadd, san, etc)

In the Forums, there are some older posts where they had UAC running on the VM and turned it off and the Job then worked
https://forums.veeam.com/veeam-backup-replication-f2/failed-to-open-vddk-disk-is-read-only-mode-t5905.html (among other things)

and a time sync issue with Veeam:

https://forums.veeam.com/vmware-vsphere-f24/fix-for-failed-to-open-vddk-disk-t37002.html

and a somewhat similar (‘datasync’ error) here on the Hub:

Look at those and see if anything helps. Otherwise, maybe a Support case.

 

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