Tag: Virtual Disk

Surface Pro Storage Spaces Boot

Boot from Storage Spaces Virtual Disk in Windows 10

A couple of weeks ago I got my new Microsoft Surface Pro, I decided to go with the 1TB version to have enough space.

Surface Pro Storage

After the first minutes of setup I quickly wanted to run disk optimization, which for SSDs usually does quick trim operations. In my case this was running way longer then on my Surface Book, so I checked what was going on, and I realized that it was running Optimization on a Storage Spaces Virtual Disk, which is kind of strange.

Surface Pro PowerShell Storage Spaces Boot

I checked the disk configuration and really, my Surface Pro (2017) does have a Storage Spaces Virtual Disk which it boots from. The Storage Spaces Pool does include two physical 512GB NVMe drives with one Virtual Disk on top configured as simple (striped) volume. Right now I don’t know how they did it, but it seems now possible to boot Windows from a Storage Spaces Virtual Disk with the Windows 10 Creators Update or some Surface team magic. Then when Storage Spaces was introduced with Windows 8, boot from Storage Spaces was not possible.


Hyper-V VHDX Format Specification v1.00

Windows Server 2012 Logo

Yesterday I posted a blog post about the new recommendations about Virtual Disks files in Hyper-V called VHD and VHDX.

Today I saw a tweet from Niklas Akerlund who posted a link to the new VHDX Format Specification v1.00.

This specification describes the VHDX virtual hard disk format that provides a disk-in-a-file abstraction.  This specification assumes that you are familiar with hard disk technologies, including how hard disks interface with the operating system or a virtual machine and understand how data is accessed and laid out on the physical medium. This specification is released under the Microsoft Open Source Promise (OSP) initiative to help guide development of VHDX virtual hard disk format implementations that are compatible with those provided by Microsoft.

Download: Hyper-V VHDX Format Specification v1.00


VHDX is the new format which is currently supported by Windows 8 and Windows Server 2012.

Windows Server 2012 Hyper-V: Virtual Disk VHD & VHDX recommendations

Windows Server 2012 Logo

In the new released Performance Tuning Guidelines for Windows Server 2012 you can find a lot of tuning information for Windows Server 2012 Hyper-V. One important part is the Virtual Disk chapter which is all about the VHD and the new VHDX format.

The basic key takeaways are:

  • Use VHDX every time
  • Use Dynamic VHDX

The VHDX format:

VHDX is a new virtual hard disk format introduced in Windows Server 2012, which allows you to create resilient high-performance virtual disks up to 64 terabytes. Benefits of this format include:

  • Support for virtual hard disk storage capacity of up to 64 terabytes.
  • Protection against data corruption during power failures by logging updates to the VHDX metadata structures.
  • Ability to store custom metadata about a file, which a user might want to record, such as operating system version or patches applied.

The VHDX format also provides the following performance benefits (each of these is detailed later in this guide):

  • Improved alignment of the virtual hard disk format to work well on large sector disks.
  • Larger block sizes for dynamic and differential disks, which allows these disks to attune to the needs of the workload.
  • 4 KB logical sector virtual disk that allows for increased performance when used by applications and workloads that are designed for 4 KB sectors.
  • Efficiency in representing data, which results in smaller file size and allows the underlying physical storage device to reclaim unused space. (Trim requires trim-compatible hardware.)

When you upgrade to Windows Server 2012, we recommend that you convert all VHD files to the VHDX format due to these benefits. The only scenario where it would make sense to keep the files in the VHD format is when a virtual machine has the potential to be moved to a previous release of the Windows Server operating system that supports Hyper-V.

VHD File Type

The following recommendations should be taken into consideration with regards to selecting a VHD file type:

  • When using the VHD format, we recommend that you use the fixed type because it has better resiliency and performance characteristics compared to the other VHD file types.
  • When using the VHDX format, we recommend that you use the dynamic type because it offers resiliency guarantees in addition to space savings that are associated with allocating space only when there is a need to do so.
  • The fixed type is also recommended, irrespective of the format, when the storage on the hosting volume is not actively monitored to ensure that sufficient disk space is present when expanding the VHD file at run time.
  • Snapshots of a virtual machine create a differencing VHD to store Writes to the disks. Having only a few snapshots can elevate the CPU usage of storage I/Os, but might not noticeably affect performance except in highly I/O-intensive server workloads. However, having a large chain of snapshots can noticeably affect performance because reading from the VHD can require checking for the requested blocks in many differencing VHDs. Keeping snapshot chains short is important for maintaining good disk I/O performance.

For more information checkout the Performance Tuning Guidelines for Windows Server 2012.

And check out my other post about VHD and VHDX for Hyper-V:

Update 1:

My Virtual Machine MVP colleague Carsten Rachfahl just told me that now also IDE devices can use the TRIM function for VHDX files. That means that VHDX on SCSI or IDE controller as well as pass-through disks support TRIM. The only thing which is required is trim-compatible hardware.

Update 2:

Even the GUI in Windows Server 2012 and Windows 8 recommend Fixed size for VHDs and Dynamic expanding for VHDX.

I have now server customer environment running in products for a couple of months and all are using the new Dynamic Expanding VHDX format. No problems and performance issues at all. Dynamic Expanding VHDX disks are even running faster than Fixed Size VHD files.


Virtual Machine Servicing Tool 2012 released


In July Microsoft released the beta of the Virtual Machine Servicing Tool 2012  and two weeks ago Microsoft released the final of  the Virtual Machine Servicing Tool 2012 (VMST 2012). I already did a post how you can update offline VHDs via Virtual machine Servicing Tool.

Virtual Machine Servicing Tool 2012 streamlines the process of keeping your offline virtual machines, templates and VHDs up-to-date with the latest operating system and application updates, without introducing vulnerabilities into your IT infrastructure. VMST 2012 helps you effectively manage the workflow of updating your offline virtual machines according to their individual needs.

Using features in VMST 2012, customers can service:

  • Offline virtual machines in a SCVMM library.
  • Stopped and saved state virtual machines on a host.
  • Virtual machine templates.
  • Offline virtual hard disks in a SCVMM library by injecting update packages.

VMST 2012 works seamlessly with other Microsoft technologies.

VMST 2012 is designed to work with Microsoft® System Center 2012 – Virtual Machine Manager (VMM) and with the following technologies:

  • Windows Server Update Services (WSUS) WSUS 3.0 SP2.
  • System Center 2012 Configuration Manager.

You can find the Virtual Machine Servicing Tool 2012 in the Microsoft Download Center.

Create a Windows Server 2012 iSCSI Target Server

Windows Server 8

In my Lab I don’t have a good storage which I can use for my Hyper-V Clusters. But with Windows Server 2012 Microsoft added a lot of new storage features and included a iSCSI Target Server. With the new Storage Pooling / Storage Spaces features this allows me to use a Windows Server as a great storage replacement.

This offers features like:

  • Thin provisioning
  • Data Deduplication
  • Disk aggregation
  • Storage Spaces
  • and a lot more


  • We will aggregate physical disks to a Storage Pool
  • On this Storage Pool we will create a Virtual Disk. Here we have to option to use Data Deduplication, Thin provisioning, Reliability options (Simple, Mirror, Parity), etc.
  • On the Virtual Disk we will create a NTFS volume
  • On this Volume we will create iSCSI Virtual Disks (LUNs)

Storage Overview