Last month, Microsoft released DirectStorage 1.1, which features support for GPU based asset decompression. The addition of GPU decompression is important, because it significantly reduces CPU overhead and acts as a bandwidth multiplier, allowing a greater amount of data to be transferred to the GPU in a shorter amount of time.
Several months prior, Phison made an announcement that would prove to be just as important. They announced the Phison IO+ Firmware, which is built from the ground up specifically for the high sustained bandwidth needs of DirectStorage. Currently, the Phison IO+ Firmware is only available in one drive - the Sabrent Rocket 4 Plus-G.
We had a chance to test Sabrent's new DirectStorage optimized SSD recently with two demos that support DirectStorage. The first one tests a bulk load, which simulates a game load scenario, and the second one tests the sustained bandwidth capability of the SSD. We also provide results of Phison's in-house synthetic DirectStorage benchmark for 10 different SSDs, courtesy of Tweaktown. This synthetic benchmark does not support DirectStorage like the previous two demos do, but it does accurately simulate a DirectStorage workload over the course of many hours.
Check out our video with the results, and continue reading the review below.
In the bulk load demo, the Sabrent Rocket 4 Plus-G reaches a total bandwidth of over 18 GB/s with GPU decompression, while the Gen3 drive is only around 8 GB/s. NVMe SSDs within the same generation perform roughly the same in this demo, but it's interesting to see the difference between a Gen4 and a Gen3 drive.
The more interesting results come when running the Expanse demo. This demo was developed by Intel as an asynchronous texture streaming solution. The demo supports both DirectStorage and Sampler Feedback Streaming, and uses just 200 MB of a 1 GB, despite 350 GB of total texture resources. It is continuously streaming assets, and as such, it is a great benchmark for a drive's sustained bandwidth in a DirectStorage workload.
As you can see in the video, the Sabrent Rocket 4 Plus-G maintains a higher bandwidth than the WD SN850X (around 6.9 GB/s vs 6 GB/s.) This is very impressive, but it may also be surprising for many readers. The WD SN850 was regarded by many as the best gaming SSD. Mark Cerny famously endorsed it as the best expansion SSD for the PS5. The SN850X is a newer and upgraded version of the SN850 that features Game Mode 2.0, which aims to provide the same benefits as the Phison IO+ Firmware. That is, high bandwidth and improved sustained performance with smart scheduling. Yet, it still falls short of what Sabrent's new gaming SSD can deliver.
Expanse is designed to stream in higher quality textures based on the capabilities of your SSD. Sabrent's new drive is able to load higher quality textures as a result of its superior performance, and so the frame rate will naturally be lower, as the higher quality assets are more demanding to render by the GPU. In games, where you manually set your desired level of detail, if you set it higher than what your drive can handle, you may experience stuttering or a general degradation in DirectStorage games.
High bandwidth is important, but so is the ability for a drive to maintain that bandwidth. As you see from the graph towards the end of our video (courtesy of Tweaktown) the Sabrent Rocket 4 Plus-G not only has the highest bandwidth in Phison's in-house synthetic DirectStorage benchmark, but it also has the best sustained performance. It even outperforms the Optane P5800X, a drive that costs anywhere from $1000-3000!
This level of performance is unlocked by Phison IO+ Firmware, which was specifically designed for DirectStorage. It optimizes performance for random reads with block sizes of 32-64k or greater, and ensures that the drive will be able to sustain that performance by eliminating block level read disturb through smart scheduling and adaptive wear algorithms. Constant read requests can lead to bit errors over time, which can result in a momentary but significant drop in bandwidth. With DirectStorage constantly hammering the drive with read requests, it will be more important than ever that your drive can avoid such bit errors, and this is exactly what Phison IO+ Firmware was designed. At present, there is no consumer NAND Flash based drive that can match the Sabrent Rocket 4 Plus-G when it comes to the combination of high bandwidth and sustained performance.
Some of you may be thinking that a constant stream of 4, 5, or 6 GB/s from disk is a pipe dream. However, those in the industry who have been working alongside Microsoft on the DirectStorage API paint a different picture.
Intel, who developed the aforementioned Expanse demo, shares their vision for a new game design paradigm:
Intel envisions a future where fast storage is valued for more than its non-volatility, and is reckoned as the last level of a memory hierarchy, to be exploited through emerging game-design technologies that stream assets in steady state. This vision of steady state data-transport from storage to GPU local memory, while rendering, is in contrast to the traditional burst of data transport at the beginning of game levels today.
In benchmark mode, Expanse acts as a proxy of future, demanding asset-streaming applications.
They go on to say:
Loading all the assets of a game level with DirectStorage is simple enough, but emerging graphics workloads load assets constantly, treating high-speed storage as a massive read-only, last-level cache.
If SSDs will be used as a massive, read-only cache that delivers data to the GPU as requested, then it is easy to see why a high level of bandwidth, and the ability to sustain that bandwidth for long periods of time without suffering from block level read disturb, will be of the utmost importance in DirectStorage titles.
Phison has the same expectations, which is why they have invested so much time and money into their IO+ Firmware. Phison has been working with Microsoft on DirectStorage for many years. The Seagate expansion SSD for the Xbox Series X|S utilizes a Phison controller. They have been working alongside other partners and game developers to understand how it will be used and what they need to develop the most robust controller and firmware for this new game design paradigm. So far, it is fair to say that they are a step above the competition in this regard.
While any NVMe SSD, and for that matter, any storage device, may theoretically work with DirectStorage, it looks like a high performance storage device will be a necessity for high detail settings and high performance in future DirectStorage titles.
Keep up to date with our continued DirectStorage coverage. With PCIe 5.0 SSDs just around the corner, we will have more coverage coming your way.
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