Hi, all!
My intention with this isn't put more gasoline on the fire, but only report the results of the tests I said I would perform in my previous post on this thread
TL;DR: This method didn't work on my system.
My host is a Acer Aspire E15, 4 GB RAM,
Intel Core i5-6200U 2.3 Ghz CPU, dual boot with
Windows 10 Home Single Language with Creators Update (1703 version) and Ubuntu 16.04.
VirtualBox in Windows is 5.1.22 r115126. In Ubuntu is 5.1.4 r110228 (more on this later).
My guest is a Windows XP machine, 1 GB RAM, and 1 CPU assigned, without any advanced option enabled.
This guest's vhd (virtual hard disk) is an .vmdk file, dinamically allocated, with 15,00 GB total size, and 14,23 actual size.
I've made four clones:
a) 1 converting the vhd to .vdi format, with dinamically allocated size.
b) 1 converting the vhd to .vdi format, with fixed size.
c) 1 keeping .vmdk format, with dinamically allocated size, and the last one.
d) 1 keeping .vmdk format, with fixed size.
I've made not so scientific benchmarks, measuring the time between the click on start button at VirtualBox manager, and the first functioning click in the guest's start menu.
The measurement of the original one is 3m48sec
The startup times from the clones float arount 3m50sec and 4min10sec. I've took care to measure the second boot, since the first one will be a little bit bigger, because Windows recognize the vhd as new hardware.
To give an idea, the same original guest, that in Windows now spends almost 4 minutes to start, boots in 28 seconds in Ubuntu. This was the performance I had before on Windows 10 (maybe a little bit bigger, but booting within 1 minute), and this is what I'm expecting now.
When I did my first post on this topic, I didn't had the Creators Update yet. After I've downloaded it, VirtualBox stopped working completely. Even the virtual connections disapeared. The solution from my problem was download and install the newest version (5.1.22).
I've noticed this same slowness on other machines I have around, one with more robust specs. As a side note, I'm experiencing the same problem with VWware Player as well, so I'm convinced this is a Windows 10, not VirtualBox problem.
Before someone suggest it, I can't switch full time to Ubuntu now
. Although the idea amuses me, and I had used this setup until last year, now I need some "unvirtualizable" software, so I spend more time on Windows than in Ubuntu.
Last, I would like to thank MariusFilo, socratis, mpack and everybody who post something on this forum.
Everyone is trying to help, in a way or another.