@OhSoNoob I've used XOSTOR on top of MDRAID and it seemed to work well for me during my testing. I ran tests of it on top of MD RAID 1, 5, and 10 (MDRAID's "RAID 10" which isn't really RAID 10) and had good luck with it. The XOSTOR is really adding a second layer of redundancy at that point, similar to MDRAID 5+1 builds so is almost overkill. Almost.
Where I see the most benefit from XOSTOR on MDRAID would be on top of RAID 10 or RAID 0 arrays. Depending on the speed of your drives, you might get some benefit from the increased read speed (and read/write speed for RAID 0). In addition, RAID 10 would give you some additional redundancy so that losing a drive wouldn't mean the loss of that node for XOSTOR's purposes, possibly making recovery easier.
The ability for some redundancy might also be useful for a stretched cluster or some other situation where your network links between XOSTOR nodes isn't as fast as it should be; The ability to recover at the RAID level might be much faster than recovering or rebuilding an entire node over a slow link.
@ronan-a, I'm not sure if you remember, but the very first test of XOSTOR I ran, shortly after it was introduced,, were on top of RAID 10 arrays. I kept that test cluster alive and running until equipment failure (failed motherboards, nothing related to XOSTOR or MDRAID) forced me to scrap it. I had similar teething pains to others while XOSTOR was being developed and debugged during the test phase, but nothing related to running on top of MDRAID as far as I could tell.
