Hyper-V - Creating a large fixed disk - EXTREMELY Slow

Question

Hey everyone, after posting another question here, it seems I have to create a fixed disk in order to get one 700GB.

I have shut down the machine (which basically has nothing on it), and gone to convert to a fixed disk. It is going EXTREMELY slow - if my calculations are correct at the rate its going it will take ~2 days to complete. Its been going for about 6 hours and its about 10% complete. I'd like to continue setting up my server and start using all of the space.

Is this normal? How can I speed this up???

Thank you,

score 10 · Accepted Answer · edited Aug 21 '12 at 17:36

By default, when you create a VHD, the creation process zeros out the data as it builds the file.

MS released a tool to create VHD's very quickly which bypasses the zero out process.

Example

To create a 100 GB VHD, use something like:

.\VhdTool.exe /create '.\Virtual Hard Disks\SRV-EXCHANGE_Backup.vhd' 107374182400

It will take only seconds to complete.

Output

PS C:\VMStorage> .\VhdTool.exe /create '.\Virtual Hard Disks\SRV-EXCHANGE_Backup.vhd' 107374182400
        Status: Creating new fixed format VHD with name ".\Virtual Hard Disks\SRV-EXCHANGE_Backup.vhd"
        Status: Attempting to create file ".\Virtual Hard Disks\SRV-EXCHANGE_Backup.vhd"
        Status: Created file ".\Virtual Hard Disks\SRV-EXCHANGE_Backup.vhd"
        Status: Set the file length
        Status: Set the valid data length
        Status: VHD footer generated
        Status: VHD footer written to file.
        Status: VHD header area cleared.
        Status: Complete
PS C:\VMStorage>

To add to Andy's response, the blog entry [Why does it take so long to create a fixed size virtual hard disk?](http://blogs.msdn.com/virtual_pc_guy/archive/2008/12/10/why-does-it-take-so-long-to-create-a-fixed-size-virtual-hard-disk.aspx) by the Virtual PC Guy, provides some background explanation as to why it takes so long to create a fixed VHD. `The reason why this takes so long is that when we create a new fixed-size virtual hard disk we take the time to explicitly zero-out all of the disk space that is being assigned to the new file.` — Reuben, Sep 07 '09 at 05:54

score 0 · Answer 2 · answered Jan 26 '15 at 12:04

0

If you are looking for a fast VHDX creation tool consider the Systola VhdxTool: It works almost like VHDTool but for VHDX and even offers compatible command line.

answered Jan 26 '15 at 12:04

Kirill Kovalenko

109
1

Why minus this? VHDTool is no longer available; this is a vaild answer. – namezero Jun 17 '18 at 09:58

Hyper-V - Creating a large fixed disk - EXTREMELY Slow

2 Answers2

Example

Output