dd
hdparm
iotop
Tool for benchmarking IO. Can spawn multiple threads performing different kind of work.
Options worth mentioning:
direct=<bool> - uses non-buffered IO (O_DIRECT)
fio --randrepeat=1 --ioengine=libaio --direct=1 --gtod_reduce=1 --name=test --filename=random_read_write.fio --bs=4k --iodepth=64 --size=4G --readwrite=randrw --rwmixread=75