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Windows Server 8 VHDX disk format supports up to 16 TB

Managing virtual disks is a challenge with any hypervisor. In this post, Rickatron shows how the VHDX format will make Hyper-V a bit easier for large storage requirements.

Windows Server 8 introduces a new virtual disk format, VHDX. VHDX is an expanded set of features from the traditional VHD file format used in Hyper-V and Xen virtualization environments. The other mainstream virtual disk file formats are VMDK for VMware and VDI for VirtualBox platforms.

The size of up to 16TB is the eye-catching statistic. WOW! That’s huge. This is very, very welcome in times where we will be poised to move more and more tier 1 applications to virtualization platforms. While memory, processor, and network resources aren’t too difficult to manage for large VMs, disk resources can be a challenge. The 2TB limitations for virtual disk files fits most systems, but we have to tweak applications when we go above that range. Now, to be clear; working with ultra-large VMs is not really fun. But, it is a necessary evil today it seems.

The VHDX format also brings a metadata structure aimed at reducing data corruption and improved alignment on large sector disks. More features of VHDX include:

  • 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.
  • The ability to store custom metadata about the file that the user might want to record, such as operating system version, or patches applied.
  • Efficiency (called trim) in representing data, resulting in smaller files size and allowing the underlying physical storage device to reclaim unused space.

Note: the above bullet points are reproduced from the Windows Server 8 Reviewers Guide with permission.

Figure A

Creating a VHDX file

Creating a VHDX file (click to enlarge)

Does having a single virtual disk file being able to scale above 2TB appeal to you? Share your comments below.

About

Rick Vanover is a software strategy specialist for Veeam Software, based in Columbus, Ohio. Rick has years of IT experience and focuses on virtualization, Windows-based server administration, and system hardware.

6 comments
Pacerfan9
Pacerfan9

I am currently working on a project where it would have been nice to be able to go past the 2TB VHD limit. Although as physical storage expands exponentially I am sure at some point in my career 16TB won???t be enough!

laman
laman

Rick is writing as if space is unlimited and you can have 16TB whenever you need. Unfortunately the first requirement is that you have such a large physical space in place.

kennethabrewer
kennethabrewer

Just last week I used a Drobo that held 4 TB for a OS migration. We did about 250 laptops and under 5 Desktops. All the info stored on each Device was transfered to the drobo then Win 7 imaged then the old info placed back on the Device we ran out of disk space in 7 days. A depote server was used I belive in this formate

Kenton.R
Kenton.R

Supposedly, 3.0 is going to add the ability to do VMware-esque live storage migrations. Better yet, it'll allow you to do that without requiring any shared storage between the hosts - something VMware doesn't do yet. I still plan to withhold my applause until I can see how it performs for myself. Anybody actually created a 3TB drive and performed a migration yet?

Craig_B
Craig_B

The screen shot points to a past article on VMware VMFS-5.

b4real
b4real

Sorry Craig -> Fixed now! Rickatron.