Ceph

http://git.kernel.dk/?p=fio.git;a=summary
http://freshmeat.net/projects/fio

"fio is an I/O tool meant to be used both for benchmark and stress/hardware verification. It has support for 13 different types of I/O engines (sync, mmap, libaio, posixaio, SG v3, splice, null, network, syslet, guasi, solarisaio, and more), I/O priorities (for newer Linux kernels), rate I/O, forked or threaded jobs, and much more. It can work on block devices as well as files. fio accepts job descriptions in a simple-to-understand text format. Several example job files are included. fio displays all sorts of I/O performance information. Fio is in wide use in many places, for both benchmarking, QA, and verification purposes. It supports Linux, FreeBSD, NetBSD, OS X, OpenSolaris, AIX, HP-UX, and Windows."

If it works well, add it to ceph-qa-suite, to run against filesystems (cfuse, kernel client, ext3-on-rbd) and block devices (rbd).

It's packaged in Ubuntu etc already.