I see tar files used with compression pretty often, usually gzip or xz. That can mess up the ability to seek around in the tar archive and build a good index.

I see tar files used with compression pretty often, usually gzip or xz. That can mess up the ability to seek around in the tar archive and build a good index. I use tar.gz as my go-to archive format, don't get me wrong. It's easy, well-supported, handles POSIX concepts well, and is pretty universal. But seekability isn't it's strong-suit.