there is also 'truncate'. Especially nice about truncate is the ability to create sparse files. So if you want to test how big a pool would be with three 1TB disks without actually using 3TB of allocated space: 'truncate -s 1T file1.img'. voila, a 1tb file that only takes kilobytes upon creation of a zpool.

Is there an advantage of using fallocate over say, dd to pipe random or zeroes to a file?