What disk image should I use with VirtualBox, VDI, VMDK, VHD

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Latest versions of VirtualBox supports several formats for virtual disks, but they forgot to provide a comparison between them.

Now, I am interested about a recommendation or comparison that considers the following:

  • be able to use dynamic sizing
  • be able to have snapshots
  • be able to move my virtual machine to another OS or even another free virtualization solution with minimal effort (probably something that would run fine on Ubuntu).
  • performance

asked Nov 23 ’11 at 0:28

VirtualBox has full support for VDI. VMDK. and VHD and support for Parallels Version 2 (HDD) (not newer versions) .

Answering Your Considerations

  • be able to use dynamic sizing

VDI. VMDK. and VHD all support dynamically allocated sizing. VMDK has an additional capability of splitting the storage file into files less than 2 GB each, which is useful if your file system has a small file size limit.

  • be able to have snapshots

All four formats support snapshots on VirtualBox.

  • be able to move my virtual machine to another OS or even another free virtualization solution with minimal effort (probably something that would run fine on Ubuntu).

VDI is the native format of VirtualBox. I didn’t search for any other software that supports this format.

VMDK is developed by and for VMWare, but Sun xVM, QEMU, VirtualBox, SUSE Studio, and .NET DiscUtils also support it. (This format might be the most apt for you because you want virtualization software that would run fine on Ubuntu. )

VHD is the native format of Microsoft Virtual PC. This is a format that is popular with Microsoft products.

I don’t know anything about HDD. Judging from looking at this site. Parallels is a Mac OS X product and probably isn’t suitable for you, especially considering that VirtualBox only supports an old version of the HDD format.

The format should not affect performance, or at least, performance impacts are negligible.

The factors that influence performance are:

  • your physical device limitations (much more noticeable on a hard disk drive than a solid-state drive. Why? )
  • expanding a dynamically allocated virtual disk drive (write operations are slower as the virtual disk expands, but once it’s large enough, expanding should happen less)
  • virtualization technology (hardware vs. software ; hardware virtualization helps VirtualBox and improves the speed of virtual operating systems)
  • the fact that you are running a virtual operating system. Performance is always slower than running an operating system on the host because of the virtualization process.

answered Jun 22 ’12 at 20:33

I always use VDI, as it is the native format of VirtualBox; however, using a VMDK (VMWare format) will increase compatibility with other virtual machine software.

VirtualBox will run fine on Ubuntu, so if the goal is Windows/Ubuntu interoperability, VDI would be a perfectly valid choice.

Both formats will fulfill your requirements.

As for the other two, VHD is a Microsoft-developed format, and HDD is an Apple-developed format; these are both proprietarily-licensed, so limit cross-platform support; I wouldn’t recommend them.

Mpack, explains a key performance difference between VHD and VDI here:

Having recently studied the VHD format, I would expect there to be at least a small difference in VDIs favor, most noticeable when you are comparing like with like, i.e. an optimized VDI vs optimized VHD. The reason is that the dynamic VHD format has these “bitmap” sectors scattered throughout the disk. Every time you modify a sector inside a block these bitmap blocks may need to be updated and written too, involving extra seeks, reads and writes. These bitmap sectors also have to be skipped over when reading consecutive clusters from a drive image – more seeks. The VDI format doesn’t have these overheads, especially if the VDI has been optimized (blocks on the virtual disk sorted into LBA order).

All of my comments apply to the dynamic VHD format vs dynamic VDI. Performance tests on fixed sized virtual disks is pointless since both formats are then the same (just a plain image of a disk), they just have different headers on them.

answered May 8 ’14 at 14:20

I don’t know if using vmdk would enable you to transparently run a virtual machine created in VirtualBox in VMware or not. It might. However a more universal option might be to use the VirtualBox File/Export function to create an “Open Virtualization Appliance” .ova file that can then be imported into VMware. With that approach, you can port to any virtualization system that supports .ova without caring what disk image format you use in VirtualBox.

If you need to export from the same VM at regular intervals, e.g. every day, that could be a pain. But if you only move to a different technology occasionally, it should be fine.

If you have a .vdi file already, You can test whether this works without having to create a new virtual machine. Export it to a .ova, then try importing with vmware.

answered Jul 3 ’12 at 21:22

A good reason for me for using vmdk is that Virtualbox (at least until v4.1) using VDI format has the tendency, over time, to fill the complete allocated disk space, even though the internal virtual disk usage is still much less. With Virtualbox using vmdk disks, this seems less of a problem.

But I’m talking years uptime. This might not be a problem many people encounter.

answered Jan 30 ’15 at 15:13

It s more related to the fragmentation of the guest file system than to the format itself. Enzo Jun 3 ’16 at 15:19

It depends on how you plan to use virtual disk as well. Not every VM wants a single partition on a single disk.

VDI seems to have more options (when used with VirtualBox), but as soon as you take VirtualBox out of the picture, support for VDI becomes somewhat shaky (as of late 2014).

For instance my solutions need to have maximum cross-platform support. Mounting a VDI (such as a loopback device) on linux or Windows 7 is harder and buggier than you might expect. Almost like the VDI has too many features, making it difficult to make fully conforming utilities that can operate on it.

VMDK is just less painless IMHO when you want it to work with any VM on any workstation, when you want to clone it 3 times to other systems on the network at the same time, and when you want to pry it open without launching a VM instance.

Even though I use VirtualBox 90% of the time, those few times when my disks become unaccessable in certain workflows have led me to favor VMDK for pluggable/shared filesystems.

answered Jan 8 ’15 at 4:33

Disk image files reside on the host system and are seen by the guest systems as hard disks of a certain geometry. When a guest operating system reads from or writes to a hard disk, VirtualBox redirects the request to the image file.

Like a physical disk, a virtual disk has a size (capacity), which must be specified when the image file is created. As opposed to a physical disk however, VirtualBox allows you to expand an image file after creation, even if it has data already; VirtualBox supports four variants of disk image files:

VDI: Normally, VirtualBox uses its own container format for guest hard disks — Virtual Disk Image (VDI) files. In particular, this format will be used when you create a new virtual machine with a new disk.

VMDK:VirtualBox also fully supports the popular and open VMDK container format that is used by many other virtualization products, in particular, by VMware.[25]

VHD:VirtualBox also fully supports the VHD format used by Microsoft.

Image files of Parallels version 2 (HDD format) are also supported.[26] For lack of documentation of the format, newer formats (3 and 4) are not supported. You can however convert such image files to version 2 format using tools provided by Parallels.

answered Nov 28 ’15 at 18:23

Looks like using VDI makes possible to trim disk file to its actual size VirtualBox and SSD s TRIM command support

answered Nov 19 ’16 at 0:23

While accurate it s a bit lackluster for a question that asks about the general differences between those formats, don t you think? Seth Nov 21 ’16 at 11:02





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