Volume Crashed , need help please

[Deathproof]

I have 6x 6tb hdd's that I started swapping for 6x 12tb hdd's , last night on my forth changeover the volume crashed showing two hdd's with system partition failures, i know how to log in via ssh but i don't know where to start or what commands might help , there is no back-ups as it was 30tb of data and I was unsure how that would work 

[jensmander]

Did you try the repair function? 

[Deathproof]

No I thought it might erase all previous data and create a new volume , clicked it now the hard drives are showing up fine but still no data?

Edited September 18, 2019 by Deathproof

[Deathproof]

disk 5 is part of the original raid is there a way to make syno know that