On Friday 22 August 2008, Phillip Lougher wrote:This looks very nice, but could use some comments about how the data isSquashfs has much larger block sizes than cramfs (last time I looked it was limited to 4K blocks), and it compresses the metadata which helps to get better compression. But tail merging (fragments in Squashfs terminology) is obviously a major reason why Squashfs gets good compression.
actually stored on disk. It took me some time to figure out that it actually
allows to do tail merging into compressed blocks, which I was about to suggest
you implement ;-). Cramfs doesn't have them, and I found that they are the
main reason why squashfs compresses better than cramfs, besides the default
block size, which you can change on either one.
The *default* block size in cramfs is smaller than in squashfs, but they both
have user selectable block sizes. I found the impact of compressed metadata
to be almost zero.