That is not correct. Data on all the other drives is still readable.
If you have eight 2TB drives, you have 8 TB of storage in WHS, versus 14TB in unRAID.
If you lose 2 drives in unRAID, the most you lose is 4TB of data on the drives that failed... the other 12TB is still there.
I think I understand what he was saying.
If you have 2 drive failures in WHS - As long as the data is duplicated on the drives that are still working then you can reconstruct the 2 failed drives since the data is on the other working drives.
If you have 2 drive failures in unRaid then the data that was on the 2 failed drives is just lost. Yes the other data is still there on the working drives, but that does not help the failed drives.
Been there done that.
Phil