512GB And VROC RAID Performance Testing
In the previous section, we tested the Intel Optane SSD 280GB against products with comparable price points. That meant 1TB-class NVMe SSDs. There aren't any consumer SSDs with price points similar to the Optane SSD 480GB, so we're comparing it to other 512GB-class SSDs.
The Intel 600p and MyDigitalSSD BPX represent the entry-level NVMe class, while the Toshiba RD400 and Plextor M8Pe (the add-in card with a heatsink version) land in the middle of the NVMe performance hierarchy. The Intel SSD 750 and Samsung 950 Pro make up the high-performance tier.
We have also answered your requests for RAID testing with a pair of Intel Optane SSD 900P 480GB drives in a VROC (Virtual RAID On CPU) array.
Intel X299 VROC Settings
Motherboard vendors ruffled a few feathers when they demoed Intel's VROC technology at Computex 2017. The technology brings RAID functionality on-die and allows for bootable NVMe volumes. But some of the arbitrary restrictions, including the requirement to purchase an additional dongle to use RAID 5 or non-Intel SSDs, doesn't mesh well with the enthusiast crowd.
Intel's VROC technology will work out of the box with two Optane SSD 900P drives. Because the drives come from Intel, you don't need to purchase a dongle (you've already paid the Intel tax to get this setup running). VROC only supports RAID 0 or 1 without a dongle, however, so you'll still have to purchase the dongle for RAID 5 support. We only have two drives, so that isn't a big issue--RAID 5 requires a minimum of three drives.
Assembling the VROC array on our Asrock X299 Taichi motherboard wasn't easy. VROC isn't well documented, and we believe Intel rushed it to market. We had to move our video card down to the third PCI Express slot and place our 900P SSDs in the first and fifth slots. That allowed us to check the correct boxes in the UEFI BIOS to build the RAID 0 array.
We used a 128KB data stripe, the VROC default, for the RAID 0 array. This stripe size favors sequential access patterns over random data, but this is an adjustable parameter. If your workloads consist of smaller random accesses, you can adjust the stripe size to a smaller value. Intel's PCH RAID uses a default 16KB stripe size that we often recommend for general computing.
The array came together after we worked out all of the platform limitations and had configured the software. The Optane SSD 900P drives are so fast that any latency penalties due to sub-par RAID scaling will be easy to identify.
Sequential Read Performance
The high-capacity 480GB Optane has the same performance specifications as the 280GB model. The same latency advantages at low queue depths shine through during the sequential read test.
It appears that VROC was not designed with 3D XPoint memory in mind, though. Combining the Optane drives into a RAID 0 array brings QD1 performance down to traditional SSD levels. Even at QD2, the Samsung 950 Pro is slightly faster than the Optane array. The VROC array reaches its peak performance at QD4 with nearly 5,500 MB/s of throughput.
The Samsung 950 Pro has the lowest latency of any NVMe NAND-based SSD. In this chart, you can see the 950 Pro well above the other "normal" SSDs at QD1, but the single 900P 480GB drive beats it easily.
Sequential Write Performance
Two other SSDs challenge Optane's QD1 sequential write speed but adding just one more command into the queue (QD2) is enough for the 3D XPoint technology to take off and leave the others behind.
The VROC array struggles at low queue depths again. We still measured around 600 MB/s at QD1 and 1,500 MB/s at QD2. By QD4, the array again stepped away from the single drives on its way to nearly 4,500 MB/s of throughput.
Random Read Performance
Optane destroys the normal tendencies we see with NAND-based drives. A single Optane 900P SSD grossly outperforms NAND-based products during random read workloads, particularly at low queue depths. The 900P 480GB achieves nearly 60,000 IOPS at QD1. Before Optane, we would get excited about a 2,000 IOPS increase from one product generation to the next.
VROC erases Optane's QD1 performance advantage. The array's QD1 random read performance falls to just over 10,000 IOPS. At QD2, the array shoots up to just over 76,000 IOPS. That's twice as much performance as the closest NAND-based SSD.
Random Write Performance
We see the same trends with the Intel 900P 480GB that we observed with the smaller model. Peak random write performance is about the same as a premium NAND-based NVMe SSD. It's speedy, but there isn't a huge advantage like we see in the three other corners of performance (random read, sequential read/write). Random write performance is already high with all SSDs, including those tied to a SATA bus.
Premium SATA SSDs deliver roughly 35,000 IOPS of random write performance at QD1. Hard disk drives deliver around 250 IOPS. The VROC array with two Optane SSDs only rises to 9,300 IOPS at QD1. By QD4, the array has caught up to the performance of a single SSD. It's very difficult to build up a queue full of waiting commands with drives this fast, so most of your random writes will occur at very low depths.
80% Mixed Sequential Workload
3D XPoint memory is amazing with mixed workloads. With a relatively low power controller, the 900P gives you ample headroom to tackle complex workloads. Optane technology delivers incredible performance advantages during heavy mixed sequential workloads.
80% Mixed Random Workload
During the mixed random workloads, the Optane drives overcome their middling random write speed. We know that Optane can increase server efficiency by boosting processor utilization, and its no doubt that the 900P delivers massive performance advantages over NAND-based products. The real question is if a desktop user can take advantage of the performance Optane has to offer.
We wouldn't be surprised to see many consumer Optane 900P SSDs make it into servers, due in part to their very large dose of endurance. Other SSDs lose performance in steady-state conditions, but the 900P doesn't suffer from the same dropoff– it retains its fresh out of the box performance even after we increase the write mixture. These types of intense write workloads cause NAND-based SSDs to fall flat.
We used to rave about the Intel SSD 750 series' consistent random write performance in steady state. It still does a very good job, but the 900P literally raises the bar. Given the baby steps we see with flash technology, it could take at least twenty years for it to catch up to Optane if it ever does at all.
PCMark 8 Real-World Software Performance
For details on our real-world software performance testing, please click here.
Just like on the previous page, the 900P 480GB wins or ties every application launch test. Also, like the 280GB model, the other drives are not far behind in these low-intensity workloads.
Application Storage Bandwidth
Viewing the PCMark 8 results as average throughput is a good way to gauge the systems' effectiveness. The Optane 900P basically doubles the throughput performance of the 950 Pro 512GB NVMe SSD, but that doesn't equate to twice the application loading speed. This test highlights how the operating system and today's applications can't take full advantage of next-gen memories. That ultimately restricts performance gains with Optane.
PCMark 8 Advanced Workload Performance
To learn how we test advanced workload performance, please click here.
Filling the drives with data and then running extended write workloads pushes them into a worst-case steady state, thus bringing NAND-based SSDs to their knees. Optane SSDs don't have an issue with the amount of data on the drive or workload duration.
VROC's performance is disappointing. At the very least we expected to see parity between a single Optane 900P SSD and the VROC array, but the single drive delivers much more performance in desktop applications than the array. We've yet to see true hardware RAID for NVMe, such as with a standard RAID adapter. Most NVMe RAID implementations are "soft RAID," meaning they are implemented in software in the operating system rather than through dedicated hardware components.
In contrast, VROC offloads RAID calculations directly to the processor, so it does consume CPU cycles. That means the feature competes for processor cycles with your applications. There currently aren't any hardware NVMe RAID controllers, which offload computation overhead entirely, though some have been announced. We can't help but wonder how they will compare.
Total Service Time
You need to look close to find the two Optane 900P 480GB drives because the service time for the workloads is so low. The drives are barely working during desktop workloads.
Disk Busy Time
The disk busy time test measures how long the drives work to complete tasks. This is in contrast to the previous set of charts that shows how long it took to complete the tasks. The performance advantage is lost in the operating system, application, and file system.
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