In 2015, Intel and Micron announced 3D XPoint (pronounced “three dee cross point”), a new form of high-speed, non-volatile, solid-state storage. But we’re still waiting for products that actually use the technology. The first 3D XPoint storage should hit the market this year. Branded “Optane,” Intel briefly documented (on a PDF that has since been pulled from its website) the first specs of the first of these products: the Intel SSD DC P4800X is a 375GB half-height, half-length PCIe NVMe card aimed at enterprise markets. Optane should also eventually come in 750GB and 1.5TB versions. Taiwanese site PCADV spotted the specs while they were up.
When Intel announced 3D XPoint, the company said that it would be 1,000 times faster than NAND flash, 10 times denser than (volatile) DRAM, and with 1,000 times the endurance of NAND, too, which would greatly reduce the susceptibility of 3D XPoint drives to write-induced failures. The specs of this first SSD reflect these ambitions, but perhaps not in quite the way people would have expected.
The 2,400MB/s read speed is high, but it’s not king of the hill. Introduced in 2014, Intel’s SSD DC P3700, the company’s nearest equivalent product using NAND flash technology, boasts up to 2,800MB/s reads. Samsung’s consumer-oriented 960 EVO manages 3,200MB/s read performance.
The Optane drive’s write performance, however, gives little or nothing up. At 2,000MB/s, it’s slightly ahead of the maximum 1,900MB/s that both of those flash units offer and well ahead of the comparably sized units (the 400GB Intel SSD manages a mere 1,080MB/s, while the 250GB Samsung hits 1,500MB/s).
Still, this doesn’t sound like 1,000 more performance than flash. What gives? The big difference appears to be in latency and the number of I/O operations the Optane drive supports per second. The P4800X can service up to 550,000 read or 500,000 write operations per second. The older Intel SSD can only service 450,000 reads or 175,000 writes per second and falls to just 75,000 writes for the 400GB unit. The Samsung drive clocks in at 380,000 and 360,000 read and write operations per second (falling to 330,000 and 300,000 for the 250GB version).
If raw operations per second are what you need, Optane is already looking strong. The latency figures—the time it takes to actually serve a read and write operation—also look good: the Intel flash SSD has a 20-microsecond latency for any read or write operation, whereas the 3D XPoint drive cuts this to below 10 microseconds. These numbers should hold up better under load, with Intel saying that 99.999 percent of read and write operations will be fulfilled in less than 150 or 200 microseconds (respectively), even with a queue depth of 16.
Moreover, most SSDs require a substantial number of I/O operations to be issued to the drive before they can really show off their performance. This can become readily apparent when doing things like copying small files; these are typically copied one by one, with the operating system waiting for one file to complete before starting on the next. In contrast, Intel says that Optane should be able to show off its high performance even with low queue depths. This should mean it can hit its top performance a much greater proportion of the time than flash SSDs do.
The other big improvement is in the drive’s endurance. Intel’s 400GB SSD has a lifetime rating of 7.3 petabytes written, or 10 full drive writes per day. The 250GB Samsung has a warranty that covers only 0.1PB of writes over the drive’s lifetime, about 0.1 full drive writes per day. This highlights one of the big differences between enterprise and consumer hardware. The 375GB Optane drive bumps the lifetime rating up to 12.3PB written, or 30 full drive writes per day. As such, the 3D XPoint drive should be much more robust under heavy write workloads.
Still, while these numbers do represent improvements on NAND flash, they’re a far cry from the promised 1,000-fold improvements.
The spec sheet also shows one other disadvantage of the new technology: the 3D XPoint drive draws about 18W when active, as compared to 12W for the 400GB flash SSD or 5.3W for Samsung’s 250GB drive. Replace a bunch of NAND drives with Optane and they may well go faster and last longer, but they’ll draw more power when doing so.
The price and availability of the P4800X are still unknown. In the consumer space, the revised Kaby Lake chipsets are “Optane Ready.” Intel is planning an M.2 Optane SSD for suitable motherboards, though information on that is currently non-existent.