SquashFS is a compressed read-only file system.

150X perf increase. This is the result of adding support for SEEK_DATA and SEEK_HOLE lseek() whence values. Which now allows us to use sparse file with the FS. ^[1]

cp --sparse=always big-file /

^[1]: https://lore.kernel.org/lkml/20250923220652.568416-3-phillip@squashfs.org.uk/