ZFS
en.wikipedia.org

... ZFS (previously Zettabyte File System) is a file system with volume management capabilities. It began as part of the Sun Microsystems Solaris operating system in 2001.

Large parts of Solaris, including ZFS, were published under an open source license as OpenSolaris for around 5 years from 2005 before being placed under a closed source license when Oracle Corporation acquired Sun in 2009 - 2010. During 2005 to 2010, the open source version of ZFS was ported to Linux, Mac OS X (continued as MacZFS) and FreeBSD.

In 2010, the illumos project forked a recent version of OpenSolaris, including ZFS, to continue its development as an open source project.

In 2013, OpenZFS was founded to coordinate the development of open source ZFS.[3][4][5] OpenZFS maintains and manages the core ZFS code, while organizations using ZFS maintain the specific code and validation processes required for ZFS to integrate within their systems. OpenZFS is widely used in Unix-like systems.[6][7][8]

Overview

The management of stored data generally involves two aspects: the physical volume management of one or more block storage devices (such as hard drives and SD cards), including their organization into logical block devices as VDEVs (ZFS Virtual Device)[9] as seen by the operating system (often involving a volume manager, RAID controller, array manager, or suitable device driver); and the management of data and files that are stored on these logical block devices (a file system or other data storage). ...

Yeah, there are some things that drew me to ZFS. The first was the inherent integrity checking.

Every time ZFS retrieves a block of data from the disk, it checks the checksum of that block with the checksum that was stored when that block was initially stored. If the checksum fails, then ZFS goes to the redundant storage for that block, and (this is the important part) other things happen.

Those other things involve making a new redundant copy of that block of data so that there remains the redundancy. Also (in my configuration) sending an email to inform someone that there has been a problem with a disk drive. An early warning, so to speak. This is the point where I buy a disk drive to replace the faulty one.

Oh, this is way cool.

At this point the operating system does not know of the problem because ZFS resolved it.

But when ZFS begins to have issues resolving disk drive issues within its RAID (in my experience, this is about two weeks later), then it bumps the messaging up to the OS level, and I will see FreeBSD (the OS) sending me emails about drive errors. This is not A Good Thing.

Still, no data loss at this point because of the redundancy. But there are warnings that the redundancy is beginning to fail. At this time I have the replacement drive in hand. (thank-you...www.bhphotovideo.com ).

So I replace the questionable drive with the new on and run the appropriate ZFS command to re-establish the redundancy.

With my usage of ZFS (because of my back-up strategy), I have only one-drive redundancy. ZFS allows multiple-drive redundancy.

And, regarding ZFS and FreeBSd...

If you watch videos on Netflix, guess the origin of those videos? Yeah, FreeBSD and ZFS. And major kudos to Netflix, their techies have contributed majorly back to FreeBSD and ZFS.