How I can save a voxel terrain?

Hello guys,

I have a little problem. I developed a voxel system for practicing and I want to save and load the level.
The voxels are in an byte-array.

byte[,,] voxels = new byte[1024, 64, 1024]

My first idea was to save every chunk (16 x 16 x 16) in one file. The resolution is bad. The hole world costs 10 - 20 Mb and this is to much.

I really need your help.
Thanks,
Jordan