See NEW! Cross Platform Java-Based diglloydTools IntegrityChecker for details.
Java-based IntegrityChecker ('icj') is now beta 5, and it is rocking fast.
I’ve never seen anything so fully utilize the system resources: disk I/O up to 128 outstanding buffers, multithreaded up to 64 threads and basically using everything there better than 99.9% of the apps out there. And it’s cross-platform: macOS, Windows, NAS operating environments, Linux, etc.
I had fun coding it, but maybe there are some more tweaks. The trickiest thing is optimizing for 4/6/8/12 cores and different speed drives since the interaction is complex. The program defaults do extremely well on the late 2015 iMac 5K and the late 2013 8-core Mac Pro. The main issue is that I don’t have a fast enough SSD on the 8-core 3.3 GHz Mac Pro to drive the program hard, so I have to test with dual instances on both the internal SSD and a RAID-0 stripe of two OWC Mercury Accelsior PCIe SSDs.
A cool new feature is finding duplicates; it saved me a whopping 100GB! By using the hashes, exact matches can be found unerringly and all but instantly (once the hashes are done via the 'update' command).