A. When you create a fixed-size virtual disk, the virtual hard disk (VHD) file that’s created is the size of the VHD. So, for example, if you create a 40GB fixed VHD, a 40GB VHD file will be created in the file system. Show
A dynamic VDH consumes space in the file system only as content is written to the VHD, so that if you create a 40GB dynamic VHD, a file of only a few hundred kilobytes is created. (The size of the initial file is based on the size specified for the dynamic disk. The initial file stores only the lookup table that will be used to map the virtual disk to the physical drive. A larger VHD needs a larger lookup table, so the initial VHD file size will be larger. The lookup table is about 0.0008 percent of the size of the actual VHD.) When data is written to a dynamic VHD, the OS has to first find space on the physical drive holding the VHD and update the lookup table; only then can the data be written. This multistep process delays the write operation. Because a fixed VHD allocates all the space in advance, a fixed-size VHD will perform better than a dynamic VHD. A fixed virtual disk actually performs about as well as pass-through disk access (in which a virtual machine directly accesses a physical drive or LUN) and offers the portability and backup benefits of a VHD. If you build a dynamically expanding VHD it is important to remember to set the size to match the maximum possible storage space it will use.
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Published: 05 Jan 2018 When you create a virtual hard disk, it is a good idea to make it a dynamically expanding virtual hard disk. The advantage of a dynamically expanding VHD is that the host PC sees the disk as the size you assign it -- say a 50 GB hard disk -- but the disk actually only uses as much storage space as it needs. In this example, there is a 50 GB VHD attached to the host PC, assigned as drive W:. Figure A shows the host Windows 10 OS seeing the dynamically expanding VHD as a 50 GB hard disk. Figure B shows the VHD file properties instead, which shows it is still empty because the VHD file on the host PC's hard disk drive (HDD) is only 260 MB.  Although the VHD file size is just under 10 GB, even after installing Windows 10, you must store it on a physical internal HDD or solid-state drive partition with free space greater than or equal to its total size -- 49.8 GB in the example above. This is important to understand. That is, you can create a 1,024 GB VHD on a physical partition with only 30 GB free space. You can even install Windows on it by applying an image. But when you try to boot it up, you will get a blue screen of death. Always remember the physical partition that contains your dynamically expanding virtual hard disk file must have sufficient free space to let it expand to its maximum size. Meaning if you assign 50 GB to your dynamically expanding virtual hard disk, make sure the partition where you place it has at least 51 GB free. Dig Deeper on Windows OS and management
Related Q&A from Ed TittelHow can IT assign PCs to Windows 10 servicing channels?Microsoft offers different tools to assign Windows 10 PCs to servicing channels. Learn how to assign desktops to servicing channels using a ... Continue Reading How can you perform a full Windows Update reset?When Windows Update malfunctions, IT must follow this four-step process to fix the problems. Be sure to have admin privileges before getting started. Continue Reading What to do if Windows Defender updates don't workWithout the latest Windows Defender updates, your users' desktops won't be completely protected. When update problems occur, there are several ... Continue Reading What is the difference between fixed and dynamically expanding disk?Dynamically Expanding Virtual Hard Disks. When you create a fixed size hard disk the space you specify is automatically allocated and reserved for that virtual machine. A dynamically expanding disk however, starts small and grows as needed until it reaches the maximum size you have allowed for it.
When using VHD storage What are the advantages of a dynamically expanding disk when compared to a fixed disk?The advantage of a dynamically expanding VHD is that the host PC sees the disk as the size you assign it -- say a 50 GB hard disk -- but the disk actually only uses as much storage space as it needs.
What is an advantage of using a dynamic hard drive?Dynamic disks provide volume migration, which is the ability to move a disk or disks containing a volume or volumes from one system to another system without loss of data. Dynamic disks allow you to move portions of volumes (subdisks) between disks on a single computer system to optimize performance.
What is a dynamically expanding disk?What is a Dynamically expanding Disk. This type of disk expands as data is written to it. The virtual hard disk file that is created at first is small, and it grows as and when data is added to it. This is the default type that's selected when you create a VHD. The file starts out very small with a preset maximum size.
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