don't bother with seagate externals, they overhead and die when trying to sustain 8TB of copying
you can see this for yourself if you install crystaldiskinfo and keep it running when doing the copy/backup...it gives a verbal warning that the drive is overheating
if you get a NAS or better a server, you can run RAID5 or zfs to give you drive redundancy
I have a NAS with 4 drives each of 4TB running zfs z1, giving 12TB usable...last week one drive failed, but no problem, with z1 redundancy I copied off the 12TB to a 2nd NAS, replaced the drive and rebuild the zfs vdisk...I could have kept the data in-situ and resilvered, but I felt it was safer to backup and rebuild
my server has 8x 4GB drives, giving 28TB usable running RAID5