I tried to compress 5 bam files using:
tar -czvf original_bams.tar.gz *.bam
The resulting file sizes ("ll --block-size=M") are:
8067M file1.bam 6962M file2.bam 10662M file3.bam 7794M file4.bam 7346M file5.bam 40828M original_bams.tar.gz
There's a difference of 3MB between the archive and the sum of the sizes of the bam files. Is this expected? I know that there is CRAM (which I will turn to next) but I'm surprised to see that good old .tar.gz has 0 effect?