Thanks guys for your help but I think it’s more complicated than I thought..
1. I have 8x Hitachi HUA72101 1TB drives instead of Seagates one.
2. R800 hangs when I’m trying to copy something from RAID to external drive. I can edit in FCP for whole day and it works perfect.
3. It usually hangs when I’m using Compressor.
Hangs mean that only RAID hangs…I can see folders but I can’t see any files inside..than I have to hard reset my Mac.