VHD create error. "The sector size of the physical disk on which the virtual disk resides is not supported"

Product: ProfileUnity          

Product Version: 5.7

Expires on: 365 days from publish date

Updated: February 26, 2014



When creating a VHD disk in FPC (FlexApp Packaging Console) the error is displayed:

Unable to open the virtual disk: \\Disk_Path\disk.vhd "Error: The sector size of the physical disk on which the virtual disk resides is not supported."



FPC is installed on Windows 7

Disk Type: Expandable  - (Thin Disk)

CIFS is located on NetApp (Samba) (OnTapp OS) device

Block Size” property is set to 4096 bytes - (i.e. 4K) , and not 512 Kb


Possible Resolution(s):

4K is only supported by Windows 8 and Server 2012 or later. 

ProfileUnity is installed on Windows 7 and Windows 7 can't mount/create VHD on disk with 4K block size.

Option A. NetApp's disk block size needs to be changed to standard (default) 512 bytes per block.

Option B. Update NetApp OnTapp OS version.

Growable (Expandable) VHD stored on a UNIX/Linux based NAS doesn’t  mount at login correctly.

Option C. Set “strict allocate = yes” in SMB.conf (Global setting)

Option D.  Workaround: In ProfileUnity Console in VHD setting select "Fixed" disk type (Thick)

Option E.  Workaround: Use Window's CIFS share to host VHD files. 


Steps needed on NetApp Filer to configure for correct access



set -privilege advanced

cifs options modify -vserver <vserver_name> -file-system-sector-size 512

According to support, there should be no performance implication by setting a smaller size block. It seems to be there for application compatibility reasons. If needed, a new storage virtual machine (SVM – new term for vserver starting from ONTAP 8.2.2) can be created to specify a different sector size.


This information is listed in their ONTAP documentation. Most of the VHD use case involved storing Hyper-V VHD images over SMB, per Hyper-V 2012 R2 adding support for SMB 3.0.

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