Win 7 Virtualization Hard Disk FAQ

What are the different types of VHD files?

The VHD file is divided into three types that can be created using Hyper-V Manager or by using the Windows Disk Management tool in Windows 7:

1. Fixed VHD. The fixed VHD file is assigned a virtual disk size that is the size of the virtual disk specified when the VHD was created. For example, if you create a virtual hard disk size of 2 GB, you will create a file size of approximately 2 GB, where part of the space is used for the internal VHD structure. The size of the fixed VHD does not change as the data is written to the virtual hard disk.

2. Scalable or dynamic VHD. At any given time, the size of the extensible or dynamic VHD file is the same size as the actual data that was written to the file. The file also increases dynamically as more data is written. For example, files that support a 2 GB virtual hard disk are initially about 2 MB in size on the host file system. As the data is being written to this virtual hard disk, the file grows until it reaches a capacity limit of 2 GB.

3. diff VHD. A differential VHD is similar to a dynamic VHD, but contains only the modified virtual disk blocks of the associated parent virtual disk. The differential VHD is linked to a specific parent VHD, called a child VHD. The parent VHD file is read-only, and all modifications are made against the child VHD. The VHD file type of the parent VHD can be any of these three VHD types, including another differential VHD. Multiple child VHD files can form a chain of differences.

Why is it recommended that fixed VHD files be used in production?

It is recommended that you use a fixed VHD file for production for the following reasons:

"Because there is no need to dynamically extend the VHD file, I/O performance is the highest of the three VHD disk types." Also, if a write operation is made to a fixed VHD file, the underlying host volume of the VHD file fails to run out of all available disk space because the dynamic VHD requires expansion.

The dynamic and differential VHD file depends on multiple data writes and internal block allocation information that may become inconsistent if all I/O to the VHD file on the host volume and the physical disk are not completed and are not saved on the physical disk. This can occur when the underlying disk has run out of all storage space or when the system is suddenly powered down.

When is it appropriate to use dynamic or extended VHD files?

Dynamic VHD is useful when using a Windows image in the following non production environment: storage requirements are low and the convenience of replacing VHD files is more advantageous than the reliability of data access in the VHD. For example, a test environment can store many dynamic VHD in a network share to conserve space without allocating the storage space required for the unused portions of a similar image in a fixed VHD format. Typically, a test environment can be easily rebuilt, or a VHD image for testing can be rebuilt. Copying a smaller dynamic VHD file from a network share to a local disk is faster than a fixed VHD file that transmits the same maximum size. If you can regenerate the entire contents of the dynamic VHD from another resource, and the critical data is stored in a volume other than the dynamic VHD, you can consider using dynamic VHD in the production environment.

Iv. what happens when the parent VHD of a child difference VHD changes?

The child Difference VHD contains a modified block of data in a specific parent VHD. If the parent VHD changes or is replaced with another VHD file with the same file name, the block structure between the parent VHD and the child VHD will no longer match and the contents of the child VHD will be corrupted.

Can the parent of the differential VHD be located on a different volume or remote share than the child?

For native VHD startup, the link for the child differential VHD to the parent VHD file requires that the two files reside on the same volume. A parent disk and a child disk cannot reside on a different volume even if they reside on the same local disk. When you attach a VHD, such as an image management operation, that is outside the native VHD startup, the parent of the differential disk can be on other volumes or even remote shares.

What are the features of "Create VHD" and "Additional VHD"?

Disk Management tools (DiskPart command line tools and Disk management consoles) support creation, attach, and detach operations. Create VHD creates a new. vhd file according to the type and size specified by the option. You can view the newly created. vhd file as similar to the original disk. The attach VHD operation requires the storage system to use the VHD as a disk attached to the system. After you perform an additional VHD operation, you can use the Disk Management tool to create one or more disk partitions within the VHD and format the NTFS file system within the VHD. If the VHD already has a disk partition and a file system volume when performing an additional VHD operation, the volume in the VHD is assigned a drive letter and the volume is available, similar to what happens when you insert a USB disk drive into a USB connector. The additional VHD is sometimes referred to as "display VHD," because the file system in the VHD is assigned a drive letter and is displayed and available for use. (You might be able to show the VHD as a submarine surfacing and visible.) )

After you perform an additional VHD operation, the system assigns drive letters to all volumes in the VHD and makes them visible in the global namespace. Whether you can see the attached VHD volume is not limited to the current user context. All users will be able to see the attached VHD as if they were looking at a physical disk. The VHD can only be appended by a user who has permission to manage the volume (only administrators are granted by default) because the additional disk is equivalent to bringing the disk or volume online.

What file systems can the VHD use?

If you already have a. vhd file, you can save the. vhd file on any fat, exfat, NTFS, or UDFs volume. However, you can only attach a VHD that is located on an NTFS volume. Performing additional operations on a VHD on a non-NTFS volume will fail.

When you create a VHD, you can create one or more partitions in the VHD, and you can format the partitions using FAT, EXFAT, or NTFS. Additional operations make one or more volumes available in the VHD.

Eight, can Windows 7 attach a VHD that is located on a remote share?

Yes, you can attach a VHD file that is located on a remote SMB share, and the VHD file will appear as a local disk. Other remote file systems, such as NFS or FTP, are not supported. The system assigns drive letters to the volumes contained in the VHD, and these volumes are available to all users on the local system, depending on the security permissions of the data within the VHD volume. The remote VHD add-on supports remote image management.

Can you use NTFS compression or encryption for VHD files?

The NTFS-compressed VHD file on the host volume will not be attached as a virtual hard disk. VHD files encrypted with Encrypting File System (EFS) on the host volume cannot be attached as virtual hard disks either. VHD files that are compressed or encrypted on the host volume will not be available for VHD native startup. However, if additional support is provided, the volumes within the VHD can use compression and encryption.

Can you use BitLocker to encrypt the entire VHD?

The VHD file can be saved on a BitLocker-protected host volume, but the VHD file located on the BitLocker protection volume cannot be used for native startup. Enabling BitLocker for volumes contained within a VHD is not a supported configuration.

Xi. what are nested VHD and what are nested restrictions?

The VHD is a file on the host volume. For example, the VHD file C:\vhd\ExampleFixed.vhd represents a fixed VHD file located in the \vhd directory on the C: volume. In Examplefixed.vhd, you can create a partition, initialize the NTFS file system volume, and then temporarily assign the drive letter M:. You can also create a new VHD file under M:\vhd\AnestedFixed.vhd. The second VHD file was created on the file system volume in the first VHD file. This is the nested VHD. Performing an "Additional VHD" operation on C:\vhd\ExampleFixed.vhd will make the M: Volume available. Performing an "Append VHD" operation on M:\VHD\ANESTEDFIXED.VHD will make another volume (for example "N:") available. Up to 2 layers of nested VHD can be attached. This means that you can attach a VHD within another additional VHD. However, if you attach a VHD in an additional VHD that is already another additional VHD, it will fail.

12. Can I configure two additional VHD as a dynamic disk?

A dynamic disk is a disk initialized for dynamic storage that contains dynamic volumes, such as simple volumes, spanned volumes, striped volumes, mirrored volumes, or RAID-5 volumes. The attached VHD cannot be configured as a dynamic disk.