+random_generator=str Fio supports the following engines for generating
+ IO offsets for random IO:
+
+ tausworthe Strong 2^88 cycle random number generator
+ lfsr Linear feedback shift register generator
+
+ Tausworthe is a strong random number generator, but it
+ requires tracking on the side if we want to ensure that
+ blocks are only read or written once. LFSR guarantees
+ that we never generate the same offset twice, and it's
+ also less computationally expensive. It's not a true
+ random generator, however, though for IO purposes it's
+ typically good enough. LFSR only works with single
+ block sizes, not with workloads that use multiple block
+ sizes. If used with such a workload, fio may read or write
+ some blocks multiple times.
+