WD 4TB Sharespace support Seagate 2TB HDD?

4x2TB Cavier Green HDDs will be fine and you can set this up as RAID 5… As for transferring your 4x1TB drives to a different NAS box, I don’t think that will work… WD ShareSpace utilises some of the space on your HDDs for base system, ths won’t work else where… I suggest you transfer your files off first then set up your new 8TB system and transfer them back on this… You could use your spare 4x1TB HDDs as an initial back up once formatted…