Creating a Linux virtual machine on dynamic vhdx file creates huge file on formating

Hello,

we just created a virtual machine on Windows Server 2012 R2 on a dynamic vhdx file.

When the operating system (Rehat 5) formats the filesystem (100GB of size), then the vhdx file explodes to 21 GB, although no data is written to the disk.

Did someone experience a similar issue? And how to avoid such space waste. If we write additional data in the virtual machine, then the vhdx expands again and gets even bigger then the 21 GB.

Thanks,

Thomas