I have installed Bluestacks 4 android emulator on my 64bit Windows PC. I have not installed many apps but in the data folder it is using about 29GB of data. In the folder Program Data/Bluestacks/Engine/Android, I can see Data.vdi and Data_0.vdi, The second one is 27.4GB and fomer is few 100 MBs. My question is what could be the reason for such large file size? Is there a way to clear unnecessary data from bluestacks?
BlueStacks is a virtual machine using image files that contain the whole "persistent memory" that is available to the virtual Android device.
Such virtual image files can be crated in two ways:
When creating the virtual machine you can decide of much memory (persistent not RAM) you assign to that virtual machine. And to make this space available an image file is created of the chosen size. The file internally is then formatted as needed by the virtual machine and contains a lot of free space, but this free space is only visible inside the virtual machine. From the outside from the beginning on the full virtual disk size is allocated in form of a file
To avoid allocating a full virtual disk size some virtual machines allow to allocate space on demand. This means that if the virtual machine writes data to a sector of it's virtual disk the will be appended to the virtual disk image the first time it is written to. The main problem is that the BlueStacks is not aware which sector has been written before or not, hence if you write and delete files inside BlueStacks other sectors may be written and so the image file is growing larger the more often you use BlueStacks.
VirtualBox contains command-line tools that allows to compress images that have grown too large but don't contain much data. But that is no longer an Android topic. Search Superuser.com for how to trim/compress VirtualBox images.