The tar command historically has been one of the few commands that doesn't follow the Unix utility syntax guidelines.
The standards page for tar says:
Use the first file operand (or the second, if b has already been specified) as the name of the archive instead of the system-dependent default
While the syntax guidelines include this:
One or more options without option-arguments, followed by at most one option that takes an option-argument, should be accepted when grouped behind one '-' delimiter.
So while the command you typed,
tar -vcfz dvr_rdk_v1.tar.gz dvr_rdk/, would be fine on older versions of tar, certain versions of tar that are written to strictly follow the utility syntax guidelines will parse this to mean "use
z as the file argument to
-f". So you should use the following to be portable:
tar -cvzf dvr_rdk_v1.tar.gz dvr_rdk/