Monthly archives "May 2014"

Resizing VHDX – Online

HyperV now supports online resizing of VHDX. A VHDX disk which is used by a VM can be resized and without restarting the VM, This is really an important feature which will allow flexibility on expending or shrinking VHDX on the fly as per the requirement.


VHDX – the ability to expand and shrink virtual hard disks is exclusive to virtual hard disks that are using the .vhdx file format. Online resizing is supported for VHDX disk types, including fixed, differencing, and dynamic disks. Virtual hard disks that use the .vhd file format are not supported for resizing operations.

SCSI controller – the ability to expand or shrink the capacity of a virtual hard disk is exclusive to .vhdx files that are attached to a SCSI controller. VHDX files that are attached to an IDE controller are not supported.

Irrespective of the Generations – Gen1 or Gen2, Online Resizing will work fine if the prerequisites are met.

Lets try this on a Gen1 VM with a SCSI Disk.

G1 VM - BeforeResize


The DISK1 in the above screen shot is a SCISI Disk


Get-VM VMName |Get-VMHardDiskDrive -ControllerType SCSI |Resize-VHD -SizeBytes 500GB





Now the VHDX is expanded. As the GUST OS on this VM is Windows 2008 R2, To get this change reflected on the VM, From DISK Management , Initiate a RESCAN. With Windows Server 2012, This change will get reflected immediately without a rescan.


After Resize – 500 GB


If its a GEN2 VM, Its more easy as the default DISK which is getting created is a SCSI Disk. So even a System Drive can be expanded.



Gen2 VM – Before VHD Resize



Get-VM VMName |Get-VMHardDiskDrive -ControllerType SCSI |Resize-VHD -SizeBytes 1TB



Resize-VHD G2 VM


If its a Windows Server 2012 VM, the change will get reflected immediately and don’t need a rescan.



G2 VM – After Resize


The current C drive which is 100 GB can now expanded  to start using the added space.

From Disk Management -> Right Click on the volume which needs to be extended

Select Extend Volume

Extend Volume

Extend Volume


The maximum available space will be set by default , how ever this could be reduced as per the requirement.

DISK Management - Extend-Volume -  Configure Size

DISK Management - Extend-Volume -  Summary

DISK Management – Extend-Volume – Summary

And now the C Drive is 1 TB.

DISK Management - After extending volume

DISK Management – After extending volume


Explorer View

Cheers !


Hyper-V Dashboard – 500+ downloads

Its a special day for me. My Hyper-V Dashboard crossed 500 downloads in three months. Thanks for all those who have downloaded, commented, tweeted and provided me feedback over email.


Cheers !


HyperV Dashboard

HyperV Dashboard





Hyper-V Clusters crashing… Due to network disconnects

I faced a strange issue with Hyper-V servers. My Windows Server 2012 cluster started crashing randomly. Last time, I had a similar experience but that was having a pattern. Every Friday between 1.3o PM and 2 PM, servers will crash. After digging, We realized that the Antivirus client (SEP) was having a scheduled scan running. However, after few minutes of scanning, the system will crash with BSOD. However, this issue was not happening to all nodes and the cluster was mostly up.

In this case, majority of the servers are crashing in a sequence. Started analyzing the logs and memory dumps.

BSOD - Probably caused by : VMMDHCPSvr.sys ( VMMDHCPSvr+80e6 )

Memory Dump  – Probably caused by : VMMDHCPSvr.sys ( VMMDHCPSvr+80e6 )



The second dump like this..


Memory Dump - Probably caused by : ntkrnlmp.exe ( nt!WheaReportHwError+249 )

Memory Dump – Probably caused by : ntkrnlmp.exe ( nt!WheaReportHwError+249 )


The event logs was having events which says that Network is getting partitioned. This opened a clue and started looking at the connectivity. Though servers are connected to the same switch, the servers are loosing pings with in the same VLAN frequently. This issue was specific to the communication with in the subnet and external connectivity was mostly fine.


We got our network team involved and after some analysis, we identified one Windows 2008 R2 server which was flooding the network. Disconnected this server and the issue is sorted out.

Lesson Learned – The issues in the echo system can also lead to failures. No where related with Hyper-V servers or the VMs, but got badly impacted.