WD samples Ultrastar DC SS540, cites robust demand for SAS SSDs

The NVMe interface is taking over for data centre SSD drives – but it is not wiping out the SAS protocol just yet. Western Digital has refreshed its slower SAS data centre SSD line, upping density from 64- to 96-layer NAND flash.

According to WD, SAS capacity demand is expected to grow 24 per cent annually through 2022, which is why it is worth making the Ultrastar DC SS540.

The new drive follows on from last year’s DC SS530. Both use TLC flash and have 12Gbit/s SAS dual-port capability but the new drive has fewer endurance and capacity options.

They are: 800GB, 1.6, 3.2, and 6.4TB at the 3DWPD level; and 960GB, 1.92, 3.84, 7.68, and 15.36TB at 1DWPD.

The SS540’s performance is up to 470,000/240,000 random read/write IOPS, 2.23GB/sec sequential reading and 2.21GB/sec sequential writing.

That makes it slightly slower than the DC SS530’s 2.31GB/sec at sequential reads but ever so slightly faster at sequential writes (2.2GB/sec). The SS540 is also faster at random read IOPS, as the SS530 cranked out 440,000 and the same – 240,000 – for random write IOPS.

A WD NVMe data centre drive such as the DC SN340 pumps out data faster – 3GB/sec or so – and its read latency is 128µs, which is slightly better than the SS540’s 150µs.

However, NVMe drives will soon be able to use the PCIe gen 4 interface, which is twice as fast as the current PCIe gen 3, with its 1GB/sec lane bandwidth. This will enable performance to streak ahead of SAS drives. 

The SS540 has a five-year warranty and 2.5 million hour MTBF rating. The drive supports self-encryption based on TCG enterprise standards and FIPS validation.

The Ultrastar DC SS540 is sampling and in qualification with select customers. Mass production is scheduled for Q1 2020.