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Re: [vfio-users] setting up virtual disks



On 03/28/17 14:21, Patrick O'Callaghan wrote:
> On Tue, 2017-03-28 at 11:47 +0200, Laszlo Ersek wrote:
>> I recommend the following setup:
>>
>> - hard disk(s):          virtio-blk or virtio-scsi disk, as you prefer
> 
> I'm interested in why someone would prefer one over the other. Can you
> explain?

I prefer virtio-scsi because it supports thin provisioning (UNMAP scsi
operation); it lets me conserve space in host filesystems that support
discard (such as ext4 or xfs, for example -- there may be more). Given
the right configuration, if you delete files in your Windows 8 or
Windows 10 VM, the space is eventually released on the host filesystem.

With virtio-blk, the software stack is less featureful and thereby
thinner, which is said by some to lead to better performance. Also, as
far as I know, dataplane is only available for virtio-blk at the moment,
it is in progress for virtio-scsi. (I could be out of date on that
though.) YMMV.

Laszlo


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