Seagate has introduced the Exos M series, a range of enterprise-grade mechanical hard drives available in 30TB and 32TB capacities. The two models, the 30TB CMR ST30000NM004K and the 32TB SMR ST32000NM003K, each offer a minimum of 3TB per disk and use a standard 3.
For a full 32GB at the max sustained speed(275MB/s), 32ish hours to transfer a full amount, 36 if you assume 250MB/s the whole run. Probably optimistic. CPU overhead could slow that down in a rebuild. That said in a RAID5 of 5 disks, that is a transfer speed of about 1GB/s if you assume not getting close to the max transfer rate. For a small business or home NAS that would be plenty unless you are running greater than 10GiBit ethernet.