by Haravikk » Thu Oct 22, 2015 2:59 am
If your enclosure supports RAID5 then it should be implemented in hardware, in which case all El Capitan will see is a single big disk, so upgrading the OS shouldn't have affected you at all.
Since you think it has, then it's more likely Akitio provided you with some kind of software RAID that implements RAID5, in which case this is most likely the problem. El Capitan's new security features mean that any kernel extensions that weren't updated to support them may no longer be loading, since software RAID is probably added via a kext this may be the reason for your problems. You can verify this by downgrading to Yosemite; personally I'd recommend installing Yosemite in its own partition to test, but you'll need to find out where the software RAID came from (possibly a disk supplied with the enclosure) and install it, along with OpenZFS. If it works under Yosemite then it's El Capitan that's the problem.
For clarity, AppleRAID (OS X's built in software RAID) does not support RAID5; it only supports concatenation (joining disks "end-to-end"), striping (RAID0) and mirroring (RAID1) plus combinations of the two (RAID10, RAID01 etc.), so changes to Disk Utility definitely aren't the problem. In fact, diskutil hasn't changed at all, only the Disk Utility app (which is just a fancy GUI that seems like it no longer supports RAID).
Anyway, you may want to contact Akitio's support staff, as they may know if the problem is related to El Capitan or not, and can tell you if the RAID5 is provided via hardware or software. If the issue is with El Capitan then at least this way you will know for certain that downgrading should fix it, as it's not really something you want to just try.
If you do have hardware RAID5 then it may perform better than ZFS' RAIDZ, so it may be worth keeping, though it's important to note that RAID5 only protects against disk failure, not data corruption, while RAIDZ protects against both.
If it is in fact software RAID5 then you would be better off using a ZFS RAIDZ as it will provide better protection and performance, since you'll no longer be running both ZFS and software RAID alongside each other.
In both cases migrating to RAIDZ will require you to be able to take a full backup of the volume (so you need to get it working first) so you'll need plenty of space to do-so, but it might be worthwhile in the long run. If you don't have the space then just stick with what works, but it's worth considering in the future.