Niraj Bhatt – Architect's Blog

Ruminations on .NET, Architecture & Design

Recovering from Windows Azure Virtual Machines failures – Unable to establish RDP connection

Your ability to recover from failures is quintessential while working with any cloud platform and same applies to Windows Azure Virtual Machines. Being in preview mode you might experience some glitches around this offering. For instance, there were times when I would setup a VM and next day I wasn’t able to RDP (Remote Desktop) into it. It looked like my hard work of setting up the VM would go down the drain. But those initial struggles filled my knowledge gaps. While the stability of VMs is dramatically improvising as we approach the General Availability, below are few pointers to deal with such failures. Hope you find them useful. 

a. Restart VM: First is to restart your VM. That should do the trick whenever your VM becomes unresponsive.

b. Delete VM: In case restart doesn’t help or restart operation is failing you can try deleting and re-creating VM. If you are attempting a manual delete via Azure Portal, you should delete the underlying Cloud Service too. Cloud Service – is the container holding your VM and would become visible when you delete the VM (will detail this in an upcoming post). Deleting your Cloud Service would allow you to reuse your DNS name (as a best practice ensure that your VM and DNS names are prefixed with unique identifiers). I have seen few developers struggle and provide different names to their VMs every time they delete it, failing to realize that they need to delete the Cloud Service too. Below Figure shows how you can create a new VM by selecting an existing disk (New -> Compute -> Virtual Machine -> From Gallery)

Azure VM Disks

c. Resize VM: An alternative to deleting your VM is to change the size of your VM. This is less intrusive but might not be feasible in all the scenarios.

d. Unlock VHD / Disk: At times, after you delete your VM, the portal might show that Disk is still attached to the deleted VM. This would result into a quandary because you can’t reuse the Disk to create a new VM until it’s detached. The easier option to resolve this is to delete the disk object. Deleting the Disk object would still retain the underlying blob. After deletion you can re-create the disk object and use it to spawn a new VM. If you can’t delete the disk then your only option is to break the blob lease manually via PowerShell or using Storage Client Library (refer to this MSDN forum link for further information).

Please do leave a comment, if you have used other approaches.

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