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- Kouros
- Posts: 2
- Joined: 22. Jan 2016, 11:03
support for qcow2 format
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Postby Kouros »
Hello,
Is qcow2 format supported in the last VirtualBox release, or do i I have to use qcow format? If not will it be implented?
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- aeichner
- Oracle Corporation
- Posts: 193
- Joined: 31. Aug 2007, 19:12
Re: support for qcow2 format
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Postby aeichner »
qcow2 support is readonly only so you will be able to convert qcow2 images to another format like VDI. qcow is fully supported but I wouldn't encourage you to use it because the default block size is 4KB which has an impact on performance. VDI is the best format to use with VBox because of the low overhead and other software like qemu can work with it too nowadays. VBox also fully supports QED which is a better alternative to qcow/qcow2 if you can't use VDI because the default block size is 64K.
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- ske
- Posts: 1
- Joined: 12. Apr 2016, 14:52
Re: support for qcow2 format
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Postby ske »
1. Why is qcow & qcow2 not mentioned in the documentation, if they are supported?
(E.g 5.0.16/UserManual.pdf)
2. Is VirtualBox supposed to be able to boot directly from a qcow2 disk?
Readonly support sounds like it might be enough to be able to boot.
I'm wondering, because I tried to boot the FreeBSD-10.3-RELEASE-i386.qcow2 pre-installed image (which their README said was good for VirtualBox), using VirtualBox 5.0.16 (on Windows Server 2008R2). VirtualBox accepted the image without complaints when setting up the guest, but failed to boot it. The guest displayed:
FATAL: Could not read from the boot medium! System halted.
The VirtualBox log showed:
PIIX3 ATA: LUN#0: disk read error (rc=VERR_NEGATIVE_SEEK iSector=0x0 cSectors=0x1)
VMMDev: Guest Log: BIOS: int13_harddisk: function 02, error 02 !
VMMDev: Guest Log: BIOS: Boot from Hard Disk 0 failed
VMMDev: Guest Log: Could not read from the boot medium! System halted.
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- GnstheGrain
- Posts: 5
- Joined: 22. Jul 2016, 06:07
- Primary OS: MS Windows 7
- VBox Version: PUEL
- Guest OSses: ...
Re: support for qcow2 format
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Postby GnstheGrain »
ske wrote:1. Why is qcow & qcow2 not mentioned in the documentation, if they are supported?
(E.g 5.0.16/UserManual.pdf)
Just bumping this unreplied (and still actual) question's post by ske
Why wasn't this even ever addressed ?
Also, anyone could point me to some pros/cons/distinction reference to help us pick the proper Hard Disk File Format ? (virtualbox really need to add more tooltips, even the Guided mode is useless at figuring out the key differences between Hard Disk file types..)
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- mpack
- Site Moderator
- Posts: 39156
- Joined: 4. Sep 2008, 17:09
- Primary OS: MS Windows 10
- VBox Version: PUEL
- Guest OSses: Mostly XP
Re: support for qcow2 format
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Postby mpack »
GnstheGrain wrote:Also, anyone could point me to some pros/cons/distinction reference to help us pick the proper Hard Disk File Format ?
That was already said above. Use VDI, which is VirtualBox's own format, and the only format which is supported for every task.
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- Zv2J2fL3
- Posts: 1
- Joined: 1. Apr 2022, 11:30
Re: support for qcow2 format
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Postby Zv2J2fL3 »
QCOW support is flaky at best, especially if you try to use/merge snapshots. Use a better solution like kvm/qemu/lxc or stick to VDI.
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- mpack
- Site Moderator
- Posts: 39156
- Joined: 4. Sep 2008, 17:09
- Primary OS: MS Windows 10
- VBox Version: PUEL
- Guest OSses: Mostly XP
Re: support for qcow2 format
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Postby mpack »
In response to a question missed above: and despite what aeichner says, IMO if qcow is not mentioned in the docs (and I get no hits in a search) then it is by definition not supported, not even on a flaky basis. That phrase "not supported" has never meant that it is guaranteed to not work. There are plenty of unsupported features in the code that the devs have implemented on an experimental basis: if the feature ever becomes needed by paying clients then they will no doubt announce and support it (which may include finishing the implementation of it).
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