For a while I’ve noticed that Virtualbox has terrible performance when install Debian / Ubuntu packages. A little top, iotop and atop research later, and it turns out the culprit is the disk I/O, which is just ludicrously slow. The cause is the fact that Virtualbox doesn’t have "Use host IO cache" turned on by default for SATA controllers.Turning that option on gives a massive improvement to speed.

To turn "Host IO cache" : Open the Virtual Machine’s Settings dialog Go to "Storage" Click on the "Controller : SATA" controller Enable the "Host I/O Cache" setting. You may also want to check any other controllers and / or disks to see if this option is on there. Save the settings and start the VM and you’ll see a big improvement.