Controlled remote access reviews of Optane SSD give qualified yes

Analysis A burst of Optane memory reviews have come out, timed to coincide with Optane retail availability, but none of them answer the "Is it cost-effectively faster than flash?" question.

Optane is Intel's branded non-volatile 3D XPoint memory, which has lower latency access and higher endurance than NAND.

Earlier this month we saw reviews of the standalone 375GB P4800X Optane SSD, like one from PC Perspective which were based on remote access to an Optane SSD system in Intel's facilities, a server featuring a P4800X and a P3700 SSD for comparison. The PC Perspective reviewer notes: "It is worth pointing out that this testing method is not ideal and is not something we would have recommend or suggested to Intel."

The Anandtech P4800X review said: "3D XPoint memory has better endurance than NAND flash, but not enough to get away without wear levelling."

Interestingly the reviewer found: "3D XPoint memory does not have large multi-megabyte erase blocks, so a low-level format of the Optane SSD needs to directly write to the entire drive, which takes about as long as filling it sequentially. Thus, while a 2.4TB flash SSD can perform a low-level format in just over 13 seconds, the 375GB Optane SSD DC P4800X takes six minutes and 47 seconds. This is long enough that unsuspecting software tools or SSD reviewers will give up and assume that the drive has locked up."

The review points out that, "With limited capacity but the highest level of performance, this Optane SSD most closely fits the role of SLC NAND based SSDs," and says it's a fit for users needing consistently low latency, particularly with low queue depths. The endurance is not that great; "In terms of total petabytes written, the P4800X only has four-fifths the endurance of the SLC-based Micron P320h."

Prices for the P4800X look to be around $1,520, about $4/GB, more expensive than NAND GBs, but it's not yet available from etailers.

Anandtech's review concludes: "If your workload matches its strengths, the P4800X offers performance that cannot currently be provided by any other storage product. This means high throughput random access, as well as very strict latency requirements - the results Optane achieves for it's quality of service for latency on both reads and writes, especially in heavy environments with a mixed read/write workload, is a significant margin ahead of anything available on the market."

But ...

The Optane SSD is ultimately an expensive niche product. If you don't need high throughput random access with the strictest latency requirements, the Optane SSD DC P4800X may not be the best choice. It is very expensive compared to most flash-based SSDs.

It is a version one product and can be expected to improve as well as having more detailed information about its power consumption become available.

M.2 format Optane

Reviews such as those of PC Gamer and Ars Technica look at Intel's 16GB and 32GB Optane M.2 memory sticks and talk of $44 (16GB) and $77 (32GB) prices – more expensive than similar capacity NAND, less than similar capacity DRAM.

Such Optane memory is supported by Kaby Lake 200 series chipsets with Kaby Lake (7th generation Core) CPUs, as a cache for use in accelerating local disk drives; it is not a standalone SSD. The XPoint and disk form a single volume and data accessed via the cache has a dramatically lower latency than if it were accessed from disk, once the cache is loaded.

The reviewers were generally unable to do comparative tests of a similar function and cheaper NAND cache and disk, because the Kaby Lake B250 chipset used didn't support it. Although a comparison between a Samsung SSD and the Optane cache + HDD combo showed that the SSD was faster and more consistent, as it did not slow down whenever the cache had to be reloaded.

The Optane works as a write-back cache, with writes being cached in the Optane drive before being written, more slowly, to the paired disk drive.

Once Windows disk blocks were in the cache a Windows reboot took 20 seconds instead of the 56 seconds needed with a reboot from a 7,200rpm disk.

The reviewer said: "Random reads with short queue depths—the perfect workload for a cache drive—are clearly a strength of Optane relative to flash."

But a reboot from a Samsung 960 EVO SSD also took 20 seconds.

The reviewer's price thinking was revealing:

The 32GB Optane costs $77. The WD Black hard disk is $73 from Amazon right now. That's $150 in total. For $139, Amazon is selling a 250GB Samsung 960 EVO. Clearly, 250GB is not as big as 1TB. If you really need the space but you're really on a tight budget, maybe the hybrid is the way to go. But if 250GB is enough for your needs, the plain SSD is the better bet.

To be more explicit: "The 250GB SSD is going to provide a better experience (because it's always fast, rather than only sometimes fast), and it's going to do it at a lower cost."

Anandtech's reviewer cannot say that an XPoint-disk hybrid combo will be faster than a NAND-disk hybrid combo and suspects that it's not. The conclusion is that users will be better off using a full SSD rather than an Optane XPoint cache-spinning disk hybrid. ®