dd if=/dev/zero of=testas bs=1M count=1000
split -b 500M testas test.

-rw-r–r–. 1 root root 524288000 Dec 30 19:09 test.aa
-rw-r–r–. 1 root root 524288000 Dec 30 19:09 test.ab

Putting back:

cat test.* > t1

Check:
e5c834fbdaa6bfd8eac5eb9404eefdd4 testas
e5c834fbdaa6bfd8eac5eb9404eefdd4 t1