It's only really seekable if you don't compress it further. That's because a tar file gets compressed after the fact. Even with compression formats that support

It's only really seekable if you don't compress it further. That's because a tar file gets compressed after the fact. Even with compression formats that support starting decompression somewhere in the middle, you now either need an additional file index that tells you which files there are and where in the compressed stream to start reading, or you have to try and scan the while archive as you would with an uncompressed tar by seeking along the headers and hope the files are large enough that you can actually skip large enough chunks to matter. It is indeed really odd that the *nix world never came up with their own, agreed upon, indexed or at least efficiency seekable archive format. I think if one of the extensions would have added per-file compression that would have had the highest chance of success.