@rizaemet-0 this is not configurable .
before qcow2 the S3 blocks were aligned with the VHD blocks, then compressed, so changing it would have been a lot of work
now with qcow2 support almost reaching stable, we have some of the tools available to resize the block size on the file ( since qcow2 are based on 64KB blocks) , so it's not impossible, but it's still quite complex to do reliably
Could you name the provider ?