Cant update 840 EVO

Solution
You will need to backup your raid then tear down the raid so that you can update each SSD individually. Afterwards, reconstruct the array and restore from backup.
Should never RAID a SSD, as it actually impacts performance (aka slows down the RAID) unless your doing a heavy end RAID setup (RAID 5+) that would have hotswappable drives, etc. Also with just a RAID 0, your risking any 'glitch' (power flux, these updates, etc. ) will break the RAID and you lose everything, NO RAID is NOT recoverable and NO you can't 'scan and restore' the data in a RAIDed drive. Just to FYI