.tgz vs .tar.gz

Comparing the result, there is no difference between "old-style" archival of directories (by means of pipe: tar -c dir1 | gzip > arch1.tar.gz) and "new-style" (by means of integrated ability of tar: tar -czf arch1.tgz dir1).

But there is a huge difference in speed. I tried to archive a large directory these 2 ways and obtained completely the same archives. I used "time" Linux tool to measure execution time. The first method (with pipe) took about 40 minutes to complete. The second method - 12.

The reason of the difference, I guess, in usage of pipe in the first method. Shell creates a temporary file for each pipe and all stdout of one application is stored into this file. Another application gets this file as stdin. We obtain the next sequence: reading of source directory, writing pipe temporary file, reading the temporary file and writing the archive file. In the second method we have only two of these actions: reading of source directory and writing to the target archive file.