On my HD all files are renamed to a shorter form and accompanied by a md5sum file. But you can't include it so nicely in the filename. Or better said, you don't want to.
To detect random corruptions CRC is good enough. MD5 has the advantage that it is much harder to fake by an intelligent attacker but that does only matter if you're paranoid, resposible for preventing industrial sabotage in your company, or have a computer savvy little brother who might be planning to replace your hentai collection by Pokemon episodes while retaining the checksum.
Oh, and md5 is not slower. Reading the file from HD is the by far most time consuming process.