Everybody loves the high performance of NVMe SSDs, but the fact remains that packing a whole bunch of them into a server can be problematic. CPUs only have so many PCIe lanes to go around, after all. The SAS-3 interface isn't going anywhere for a while yet, and HGST's Ultrastar SS330 series SSDs makes good use of it.
These drives come in MLC and TLC varieties, although HGST further subdivides the product stack based on endurance rating and encryption capabilities. The MLC drives are available with endurance ratings of either three or 10 DWPD (drive writes per day) and capacities ranging from 400 GB to 3.2 TB. Their TLC cousins instead come with endurance ratings of either 0.5 or 1 DWPD, and capacities ranging from 480 GB to 7.68 TB. All the drives are available with options for TCG encryption, FIPS-compliant TCG encryption, or an "instant secure erase" feature.
HGST says that all of the drives are capable of putting up 2100 MB/s in sequential read performance, and 400K IOPS on random reads. That kind of throughput is possible thanks to the dual-ported 12-Gbps SAS connection. The MLC drives sport similar sequential write performance at 2050 MB/s and 200K random IOPS. As expected, write performance on the TLC drives is significantly worse at 1250 MB/s sequential and 120K random IOPS, though those numbers are still head and shoulders above any SATA disk.
HGST gives very impressive reliability figures for these enterprise-oriented SSDs. The company gives each drive a maximum write capacity ranging from 900 TB on the bottom-end to 59 PB at the top-end. HGST warranties the drives based on that figure or for up to five years, whichever comes first. The company is clear that it expects buyers to use these drives for 24x7 operation in environments up to 60°C, and specs them for a 0.35% annual failure rate.