Warn about file size limits

[Michal Suchanek]

When the disk image is stored on a fat filesystem it may easily overflow the 4G file size limit.

When that happens the VM is paused and the contents of the image is destroyed. The image is shown as having only a few megabytes in disk image manager. Using a 5G resizable image.

[Frank Mehnert]

This bug is not easy to fix. Actually we are aware of this issue and would like to detect the maximum file size at VM startup. The reason for not doing this is that there is absolutely no trusted API call for determining this limit. On Linux one can do seek to check if the file pointer can be moved beyond 4GB. But this does not work for NFS or smb shares and neither does this work for Windows hosts.

[Joe]

Isn't it possible to control this at vdi creation time, or even during openmedium (in case user moved the vdi)?

It's possible to check the filesystem of the proposed path isn't it? Eg in Win32 the GetVolumeInformation api call. And then, if it's FAT32 and the size is 4GB or greater, raise an error?

[aeichner]

3.2.6 adds a size check and warns the user if the maximum size of the VDI exceeds the limit of the filesystem.