Case# 07780854: VDDK Error Thrown during Backup Process

[FujiTech]

Receiving error:

Code: Select all

8/2/2025 8:46:07 PM :: Changed block tracking is enabled  
8/2/2025 8:46:28 PM :: Processing KT-PrintServer Error: Failed to open VDDK disk [[CSTNCTMNAS-ds1] KT-PrintServer/KT-PrintServer.vmdk] ( is read-only mode - [true] )
Logon attempt with parameters [VC/ESX: [cstvc1.cst.local];Port: 443;Login: [cst\fdbt-backup];VMX Spec: [moref=vm-27366];Snapshot mor: [snapshot-138406];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}.

In an attempt to eradicate the ongoing backup failures, see steps I have performed:
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Stopped and Started Services
Confirmed Permissions
Performed ping tests from the Proxies to the faulty host
Performed ping tests from Veeam Backup server the to host
Confirmed all datastores were online and being accessed properly
VSS was confirmed
Reviewed all relevant logs (That I am aware of).
Confirmed all switch and host ports are configured properly
Traceroute / Tracert end to end
Confirmed IP/Mask schemas
Rebooted ESXi host
Re-seated all cabling
Rescanned all vHBAs
Confirmed vSwitch Configurations

[Andreas Neufert]

Is it maybe a IDE disk instead of SCSI?

Anyway the above error can have so many different root cause that I really think you should open a Veeam support case and upload logs. The support team can have a look at it.
If you search here in the forum you will find other examples and people documented there their root casues.