Discussions specific to the Microsoft Hyper-V hypervisor
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Full Name: Anders Alstad

Problems with CBT (RCT) after upgrading to Hyper-V 2016

Post by aalstad » Jun 23, 2017 9:06 am

Case #02192834

Using 9.5 Upgrade2 on windows 2016
The host-Server is 2016 Hyper-V Edition

I have upgraded 6 servers to Hyper-V 2016, and everything was running good for some time.
But now I’m having problem with backup of one of my VM, it has 17 disk with total 74TB.

I started to get these errors:

Processing SERVER1 Error: The system cannot find the file specified. Failed to open file [D:\hyper-v\virtual hard disks\SERVER1-O_F3FAA80E-460C-4A8C-B3C7-969952F164F8.avhdx] in readonly mode. Failed to open VHDX, disk path: 'vhdx://<shadowSpec><extent path="D:\hyper-v\virtual hard disks\SERVER1-O.vhdx" shadow="D:\hyper-v\virtual hard disks\SERVER1-O.vhdx" isAutoRecovery="False" /><extent path="D:\hyper-v\virtual hard disks\SERVER1-O_F3FAA80E-460C-4A8C-B3C7-969952F164F8.avhdx" shadow="D:\hyper-v\virtual ha

I got them on 6 of the disks, and after this My backup takes 24Hours to run, and created 10Tb backup every day, compared with 700Gb before.

Backup of these 6 disks takes up to 24 hours, and the backup reads almost the whole disk.
It looks like the RCT (Native CBT) is corrupted.
I have tried to disable CBT on the backup, and it still run for 24 Hours but creates a backup of 700GB.

I have talked with Veeam Support, and I can’t say I have got any help.
All they say is try to delete the RCT and MRT files.
And to do this I have to shutdown the server.

I believe this might fix the problem now, but not the original problem.

Does anyone know of another way to reset the RCT ? Or any other help?

Andreas Neufert
Veeam Software
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Full Name: Andreas Neufert
Location: Germany

Re: Problems with CBT (RCT) after upgrading to Hyper-V 2016

Post by Andreas Neufert » Jun 25, 2017 7:48 pm

As we use the Microsoft RCT and it do not work, there are 2 options. To investigate with Microsoft or to reset it (maybe something broke at upgrade?).
You asked for some additional feedback in our support case. Our support team work on this.

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