As i mentioned in Drive for OS (not for data) , i created an additional data-partition on my system-SSD, and mounted it in WebGUI.
After creating a new share on that partition i created a directory, chown'ed it to r/w/e for vbox and vboxusers, and moved the VHDs of two VMs to that location. In the origin directories i created symbolic links pointing to the VHDs on SSD. It works without issues, and signicantly boosts the VMs performance.
The partition changes on the SSD (shrinking the root-partition to 8 GiB, recreating the extended partition and the swap-partition in it, creating a primary ext4-partition) were made with partedmagic (last free version), that i booted from USB-pendrive on my N54L.
BR
Jan