Odd Tar behavior

[Derrick Ryalls]

Greetings list, 

I just observed some really strange behavior with a tar file in my
backup script.  Using a command like tar -cf /someplace/www.tar www
(when in /usr/local) it produces a 2 Meg file.  Under webroot, there
are several files that are 500+ meg in size, so this size value is
suspect, though it only took a few seconds to create the archive.

The weird part comes in when I untar www.tar.  Suddenly all files are
there in their full sized glory, leading me to believe that I am only
saving file pointers or something.  Also, it isn't a compression issue
as I am not using compression, and the files themselves really aren't
very compressable.  Whatever the case, how do I use tar to create
reliable backups, including large files?

Thanks in advance for any pointers on this.

-Derrick