
Two possible issues I can think of...
...barring your posting commands used.
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Some tars have an absolute cap on filename length. I'm not sure what this is with GNU tar, but recursing long names into a directory should identify whether this exists at any of the likely intervals (256, 512, 1024, 2048, 4096 characters, etc.). I have encountered this problem, possibly on either tar, CD ROM (the iso9660 format also has a total name length cap), or NTFS.
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Depending on how you were selecting files for inclusion in your tar archive, you may have run into the shell quoting issues mentioned earlier. You'll find that GNU tar does allow for null-terminated filenames, to work around the problem of embedded whitespace. Some folks feed find output to tar, in which case the problem can crop up. One of the reasons I prefer tar over such alternatives as cpio and afio is that tar will handle directory recursion itself while the other tools want input fed from stdin, by means that always require heavy manpage decoding by me. Note that there are some commendable advantages to the filestructures used by cpio & afio, I'm not criticising these.
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Bill, you made an absolute statement of what tar could or couldn't do. It's demonstrably wrong for GNU tar. If you care to show methods, we might be able to identify the source of the problem. It's not what you've represented it to be.