[plug] Interesting VM trick

Russell Steicke russellsteicke at gmail.com
Mon May 26 07:29:29 UTC 2014


On 26 May 2014 14:26, Brad Campbell <brad at fnarfbargle.com> wrote:

> Then it occurred to me that QEMU does not know if I pass a full raw disk
> or a partition. It looks the same, just smaller. So I partitioned the drive
> into two, and restored the respective MBR/partition tables at the start of
> each drive partition. kpartx then looked at each partition as a partitioned
> disk and set up /dev/mapper instances for me to restore the VM's to.
>
> Now I can select either partition to pass to qemu (or both and run two
> machines side by side) and I get raw disk performance, but perfect
> separation of the machines. No more switching, and backups can be performed
> as previously, but with an added kpartx step. Windows can manage its own
> partition tables and file systems without interference.
>

Do you find that you need to use host block devices for performance?  I
generally use files as the guest block devices, set up with libvirt's
virt-manager, for my limited home VM use.  I haven't done speed testing to
see what the difference would be.



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