I recently ended up using xfs_io to generate data as fast as possible whilst avoiding the read(2) overhead. That utility takes an optional -S pattern, similar to yes(1):
$ xfs_io -c 'pwrite -S 0 -b 1M 0 512M' zeros It also has more fine-grained controls that would be overkill for yes(1), but a method of quickly generating data without having to read it is valuable. seq(1) is also sometimes useful for this, falling somewhere between repeated patterns and random. Cheers, Phil
