If one PCI Express SSD is fast, what happens when multiple PCIe SSDs are put into action? On the surface, the performance possibilities are intriguing — but are the actual costs of creating a system worth the investment, and what issues can crop up? This real-world example follows the development of a four-drive system using Samsung 950 PRO M.2 NVMe PCIe SSDs to replace a 10-drive SATA SSD-based system.
Creating a More Efficient System
Puget Systems is a specialty PC workstation manufacturer, making systems for photo and video content creation, engineering, scientific research and special applications. The high-quality PCs they manufacture include quiet gaming computers, desktops, workstations, laptops and servers. They were tasked with developing workstations to process data from a client that produces color imagery and LiDAR elevation data collection, processing and dissemination for the U.S. Army Geospatial Center. LiDAR (Light Imaging, Detection and Ranging) is a surveying technology that measures distance by illuminating a target with a laser light from a high-altitude airplane.
The Army system collects LiDAR data at 300-square-kilometers/hour, and requires considerable processing power to render the data and produce final images. Puget Systems, with help from their President Jon Bach, worked to develop new systems for processing the LiDAR data. The sets consist of data ranging from hundreds of gigabytes to terabytes.
PCIe SSDs Deliver a Dramatic Increase in Speed
After moving from quad-core desktop processors to 18-core Xeon processors, the next bottleneck was the storage throughput. The Puget Systems team looked at moving from the previous system’s SATA SSDs to an array of 10 SSDs on an LSI controller, and then investigated using the new Samsung 950 PRO PCIe NVMe drives connected to an Amfeltec PCIe sled. The sled uses a PCI Express SSD with a 16x slot to connect up to four 4x PCIe SSDs. One Samsung 950 PRO was able to hit 2,500 megabytes per second (MB/s), about the same as 10 standard SSDs, and four 950 PROs on the sled hit 10,000 MB/s — quadruple the speed of 10 SATA SSDs.
Read input/output operations per second went from 100,000 with a single SSD, to 120,000 with 10 SSDs, to 160,000 with one NVMe drive, to 165,000 with four 950 PROs. Write IOPS went from 80,000 with one SSD, to 60,000 with 10 SSDs, to 100,000 with one 950 PRO, to 120,000 with four 950 PROs. The lack of significant improvement with four 950 PROs over one indicates that the PCIe bus was saturated — using separate slots for each NVMe drive might have increased IOPS.
In actual production tasks, improvements with NVMe RAID over SATA RAID varied from 10 percent to 20x. Average render times for a 50-square-kilometer image went from 8 hours on the SATA SSD RAID system to 6.5 hours with the NVMe SSD RAID using the Samsung 950 PRO drives.
The remaining challenges were ensuring proper cooling with the 950 PRO drives in the PCIe slots, adding more capacity, since the Amfeltec sleds support only four drives (as opposed to the LSI RAID adapter’s 10 SATA drives), and getting Amfeltec drivers to work with Server 2012.
However, all the issues were resolved, and the new systems with the 950 PROs now provide a 30 percent overall improvement over the previous 10-drive systems. Current costs for the 512GB 950 PROs are equivalent to the 2TB SATA-based drives used previously, and although there’s a reduction in available capacity, the overall improvement in speed makes the new drives the best choice.
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