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Windows 8 Storage and Hyper-V – Part 2: VHDX and PowerShell
Jan 24th
This blog is part of a series that started with Windows 8 Storage and Hyper-V Part 1 – Introduction:
http://www.hyper-v.nu/archives/hvredevoort/2012/01/windows-8-storage-and-hyper-v-part-1-introduction/
VHD HISTORY
If you have been working with any of the Microsoft virtualization products, you are familiar with the Virtual Hard Disk format. VHD was introduced with Microsoft’s acquisition of Connectix and their Virtual PC product in 2003. Seven years ago Microsoft decided to make the VHD Image Format Specification available to third parties under the Microsoft Open Specification Promise.
In June 2005 Microsoft promised that the VHD file format would have a future well beyond the then prevalent virtualization products ….. and boy did they keep their promise!
The Microsoft VHD file format specifies a virtual machine hard disk that can reside on a native host file system encapsulated within a single file. The format is used by Virtual PC 2007, Virtual Server 2005 R2 and Hyper-V and the format will be used by future versions of Microsoft Windows Server that includes hypervisor-based virtualization technology. Beyond that, the VHD format is broadly applicable, because it is agnostic to the virtualization technology, host operating system, or guest operating system with which it is used.
Customers and partners who invest the VHD file format will have a clear path forward to future Windows virtualization technologies. In addition, Microsoft plans to design its systems management tools around the VHD file format for improved patching and manageability.
Since the release of Windows 7 and Windows Server 2008 R2, the VHD format became even more versatile when Microsoft promised not only to standardize the variety of container files, but also introduced native VHD. This technology made it very easy to boot from VHD and have multiple operating systems on one machine. Since then VHD’s could not only be created via the Hyper-V manager but also via the inbox Disk Manager and Diskpart. Because the VHD format was opened up a multitude of VHD tools surfaced (vhdtool, disk2vhd, wim2vhd and many more). There was no easy way to just mount the VHD from the command line so 3rd parties jumped on this as well. I should not forget to mention James O’Neill’s awesome Hyper-V PowerShell Management Library which he created when he still worked for Microsoft.
The VHD related commands in that library are:
Get-VHDDefaultPath, Get-VHDInfo, New-VHD, Compact-VHD, Test-VHD, Convert-VHD, Merge-VHD, Mount-VHD, Unmount-VHD
VHDX
During the \\build conference we learnt that Microsoft will introduce a new advanced version of the Virtual Hard Disk format called VHDX in Windows 8 (both client and server). What do we currently know about this VHDX?
Virtual Hard Disk Performance
Mar 18th
Liang Yang and Anthony F. Voellm have published an interesting article (March 2010) on the awesome performance improvements attained with the Microsoft VHD format in Windows Server 2008 R2, both in native VHD and Virtual Machine VHD.
The article describes the VHD format, compares VHD performance in Windows Server 2008 and in Windows Server 2008 R2, Native and Virtual Machine VHD performance and explains the difference in performance between fixed sized, dynamically expanding and differencing disks.
Supported and practical limits of VHD’s
|
Virtualization Feature |
Windows Server 2008 Hyper-V(RTM) |
Windows Server 2008 R2 |
|
Nested Depth (VHD in VHD) |
0 |
2 |
|
Default VHD Block Size |
512KB |
2MB |
|
Minimum VHD Size |
3MB |
3MB |
|
Number of Attached VHDs |
Limited by the virtual bus (64) |
Limited by the number of disks Windows allows |
|
Max Differencing Chain Length |
Effective = 8 Supported = 50 |
Effective =1024 Supported = 1024 |
|
Max Fixed Sized VHD Size |
2048GB(2040G via Hyper-V Manager) |
16TB(2040G via Hyper-V Manager) |
|
Max Dynamic VHD Size |
2040GB |
2040GB |
|
Max Differencing VHD Size |
2040GB |
2040GB |
For full article please go to this url:
http://download.microsoft.com/download/0/7/7/0778C0BB-5281-4390-92CD-EC138A18F2F9/WS08_R2_VHD_Performance_WhitePaper.docx)
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