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Modern cars are transforming rapidly from vehicles that bring a person from point A to point B with decent comfort, to computers on wheels. As a result, modern and next-generation vehicles—battery electric vehicles (BEVs), hybrid/plug-in hybrid electric vehicles (HEV/PHEV), software defined vehicles (SDVs), or vehicles with full self-drive (FSD)—require components that are akin to those used in computers. This not only includes high-performance application processors, but also enough memory, high-capacity storage and sophisticated I/O.
Micron’s 4150AT at a glance
Announced back in April, Micron’s 4150AT SSD is a PCIe Gen4 x4 storage device designed to meet safety, reliability, durability, and security requirements of vehicles, while also offering performance and capacity typically found in PCs and smartphones.
Micron 4150AT SSD comes in a BGA package integrating a custom controller—defined by Micron and developed by a third-party SSD controller designer—with 176-layer 3D TLC NAND 512 GB memory devices. The drive features quad-port design and supports single-root I/O virtualization (SR-IOV) to physically connect to up to four host SoCs and support up to 16 virtual machines per SoC (64 VMs in total) at the same time. Four physical ports and 64 VMs are meant to simplify storage subsystems of modern and upcoming vehicles.
The device was designed from the ground up to meet safety and reliability requirements of the automotive industry (i.e., it is ASIL-B functional safety and ASPICE L3 software quality certified, it can work at -40 degrees Celsius to 115 degrees Celsius temperatures, as well as has an MTTF of over 10 million hours).
By MRPeasy 05.01.2024
By Global Unichip Corp. 04.18.2024
Micron’s 4150AT drives are set to be available in 220 GB, 440 GB, 900 GB and 1.8 TB 3D TLC configurations, aiming for different types of cars. As for performance, the SSD enables up to 600,000 random read 4,000 IOPS (2,457 MB/s) and up to 100,00 random write 4,000 IOPS (409 MB/s).
While 3D TLC NAND provides optimal endurance and performance for client PCs and even enterprise mass storage, it is not a good fit for all applications used in vehicles. This is why Micron’s 4150AT SSD can be flexibly customized in multiple endurance groups, which includes TLC for less critical applications that need plenty of storage space; SLC for critical subroutines that need to use durable storage (20× more durable than TLC); and HE-SLC for applications like black box recording (50× more durable than TLC).
“Some of the data is written infrequently, but read frequently, so that is great for TLC to take advantage of the density,” said Michael Basca, Micron’s VP of Embedded Products and Systems. “There is other data that sits at the other end of the extreme, such as black box data that is constantly recording on different things. So, we have different endurance levels offered in SSD.”
One of the key benefits that is enabled by Micron’s 4150AT SSD, thanks to four ports and SR-IOV support for up to 64 virtual machines, is centralized storage, which is something that is generally absent in current cars. Nowadays, different SoC within a vehicle have to use different storage devices, which is costly and challenging from a development point of view.
“SR-IOV capability provides both security protection for the data that is been written, making sure that data from one domain or function is not accessible by another, whether by intent or by compromise,” Basca said. “So, that is why SR-IOV allows a direct interface for the SoC to the SSD without having to go through [a] hypervisor, which provides some significant performance benefits, about two times on the read capability.”
By using centralized storage (or at least using fewer storage devices per vehicle), automakers can reduce the complexity of their vehicles, decrease development costs by lowering pressure on engineering teams, cut production costs, improve security, decrease power consumption, lower weight, reduce total cost of ownership (TCO), and ultimately make cars better and safer, according to Micron.
“This centralized storage is aligned with the overall trend of vehicles moving from the traditional distributed architectures to these centralized architectures,” Basca said. “So, this is one more tool in the toolbox to help accelerate that transition. There [are] a lot of benefits for vehicles on the road, the reduced cabling, the reduced weight of the vehicle, are quite significant. You know, when we look at the up to 40 pounds, when you think about the overall energy efficiency of that, it becomes quite dramatic.”
Reducing complexity and storage requirements
Nowadays, different subsystems and SoCs in a car usually have their own storage devices, which greatly complicates automobiles and makes them more difficult to develop, manufacture and serve. On the software side, engineers must squeeze their code and data into smaller drives as car manufacturers would prefer to save on SSDs. Even if a car manufacturer decides to install one high-capacity SSD and use it with multiple SoCs, it will need to use an automotive-grade PCIe switch and a supervisor, which adds costs and lowers performance, according to Micron.
“Today, each SoC has its own dedicated storage, right, whether that is eMMC, UFS or a single port SSD,” Basca said. “[Each] particular domain [may] cause a lot of work for the engineers to scramble and really try to squeeze in [their] code, they [may have to] compromise some features and capability […] trying to fit within that given density. At the other end of the extreme, a lot of these devices end up having additional storage available, [but it is not] available for other systems within the car. So, bringing that together into a centralized storage model obviously changes all of that dynamic.”
In fact, many subsystems within a car tend to use the same data (e.g., maps). Today, that data must be recorded on different drives (with unnecessary redundance), which increases storage requirements for cars. But with four PCIe x1 ports, SR-IOV, and with private and shared namespace capabilities, it is possible to share data between different functions of a car, which simplifies vehicles both on the hardware and software side of things. Meanwhile, since some namespaces can be set to private and therefore accessible for only one or two VMs—whereas others can be shared between multiple VMs—there is no compromise in terms of security. Furthermore, this also helps lower power consumption and TCO.
“The main advantages we see are the reduction of storage footprint and power consumption, lowering the average cost/GB in auto and TCO,” said Thibault Grossi, a senior technology and market analyst in the memory division at Yole Group. “It also enables the possibility of sharing data across different controllers/SoCs, avoiding unwanted data redundancy near different controllers.”
“Having a shared storage resource also brings flexibility in the way the storage resources are allocated to the different SoCs and VMs. For example, this could ease OTA upgrade management,” said Adrien Sanchez, a senior technology and market analyst in the computing and software division at Yole Group.
The path to SDVs: Fewer SoCs, fewer ECUs, fewer drives
Traditionally, each function within a vehicle was assigned to a separate ECU and there were multiple SoCs with their own memory and storage that were each responsible for a certain function. Connecting all those SoCs to a single drive is possible on paper, though it is hard to tell whether four ports (even with 64 VMs for support) is enough and optimal. For SDV, it may well be enough.
“If we consider all the ECUs in Cockpit and Advanced Driver Assistance Systems/Autonomous Driving [ADAS/AD] that may embed managed NAND, four ports could, in some cases, be insufficient,” Sanchez said. “In the Cockpit, functionalities include the instrument cluster, connectivity, infotainment and head-up display. In ADAS/AD, functionalities include fusion/central controller, front cameras, LiDAR, and DSSAD, which requires dedicated ports for effective data transmission.”
However, as automakers transit to more advanced SoCs, they reduce the number of processors and storage devices per vehicle, but increase the number of applications run by a single processor.
“If we take the example of the cockpit domain, with the move towards centralization, multiple functions—such as media players, parking assistance, voice assistants, navigation, in-vehicle connectivity, audio processing and head-up displays—can now be managed by a single hardware device designed around one main SoC,” Sanchez said. “This is also true in other domains.”
This changes requirements for automotive storage: the number of drives goes down, but the new storage devices must be able to serve multiple applications at once.
“This consolidation of functions onto a single SoC not only reduces hardware complexity but also allows for the use of virtualization techniques, enabling one SoC to run multiple virtual machines,” Sanchez explained. “Consequently, the number of ‘applications’ running on the domain controllers will experience a substantial increase, and this does not even consider the fact that new functions/applications could be added at the owner’s request after the vehicle is acquired.”
Furthermore, as the industry transits to SDVs, centralized storage will not only be more prevalent, but a preferrable solution. This is where 4150AT’s four ports may be enough.
“As we are already in the era of domain centralization and moving towards full centralization with zonal controllers, we are seeing domains being managed by one ECU, possibly using one SoC,” Sanchez said. “This shift toward centralized architecture is a prerequisite to transition to a software-defined vehicle. This could mean one SoC for the Cockpit, one for ADAS/AD, and one for the vehicle powertrain and dynamics, or a central unit with IVI and ADAS SoC plus zonal controllers, suggesting that four ports per drive may be enough.”
Is 2 TB enough for a modern car?
While modern cars have a lot of compute and multimedia capabilities, their storage requirements are not as huge as one might think—100 GB is enough for Level 2++ autopilot, whereas Level 5 FSD will need around 1 TB, according to estimates by Yole Group.
“We currently estimate that the amount of storage required for L2++ (Tesla Autopilot level, for reference) is in the order of 100 GB and over 1 TB for Level 5,” Sanchez said. “Beyond storage for models and ADAS software, vehicles with Level 3 and above may need storage for data storage systems for autonomous driving [DSSAD] and sensor data recording [blackbox], which would require continuous data logging, requiring petabytes of total bytes written [TBW] endurance. We estimate the associated additional storage requirement to be in the range of 512 GB to over 1 TB [in TLC]. The use of (p)SLC, which has at least ten times higher PE performance, could help reduce the required GB.”
As for infotainment, experts from TechInsights believe that 64 GB to 1 TB of storage is good enough for infotainment systems.
“Modern infotainment systems typically require 32 GB to 128 GB of storage, with systems in mid-range vehicle models having infotainment systems with storage in the 64 GB to 128 GB range,” said Greg Basich, associate director of automotive infotainment and telematics at TechInsights. “Stellantis’s Uconnect 5 infotainment systems have 64 GB of flash storage and 6 GB of RAM. In addition, there are vehicles in the premium segment that have more storage, of course. Some have IVI systems with 256 GB of storage or more. Tesla is an outlier example where a vehicle owner can buy an optional 1 TB SSD, but this is because Tesla integrated the Steam store into its vehicles, and games can require hundreds of GBs of storage. Having 1 TB of storage for infotainment systems is not typical for most automakers as of 2024 though.”
When it comes to telematics electronics control units (TCUs)—the units that manage communications within cars and with the outside world—their storage requirements vary greatly too from 8 GB to 256 GB, depending on their capabilities.
“Storage requirements for TCUs vary widely,” Basich said. “There are many that just have 8 GB of storage in the market, but there are some devices that have far more, in the 128 GB to 256 GB range. This varies widely based on individual automaker requirements and what the OEM is using the device for.”
Micron itself positions its 4150AT SSDs for cars with Level 3 capabilities and above, but some of these drives will be used for Level 4 and Level 5 vehicles.
“The drive overall is targeted for Level 3 and above,” Basca said. “So, a lot of today’s vehicles, Level 2, Level 2+, are quickly migrating to level three and beyond. Certainly, this drive, I expect we will find some homes in Level 4. Those are pretty small markets [for now]. So, we wanted to make sure that that we had a product that was going to be sweet spot for a big part of the market overall.”
Meanwhile, Level 5 cars may need 2 TB or more storage, according to Micron. The estimate may be based on the fact that Level 5 cars will primarily be premium vehicles.
“Level 5 requirements are quite significant,” Basca added. “2 TB is what we have met in the engagements that we have had at that spot, but certainly, over time, depending on the specific time horizon, we expect them to continue to grow beyond 2 TB. I think you will expect us to match the needs in that part of the market over time.”
Safe and secure
But while a 2 TB SSD with four ports and SR-IOV may be enough even for a Level 5 car, a natural question that arises is whether it is safe and secure to have only one storage system for everything in a car. For now, analysts do not seem to have a definitive opinion on whether an SSD like Micron’s 4150AT will support everything needed to power a modern vehicle or an upcoming SDV—it is not compliant with ASIL-C and ASIC-D safety requirements for critical systems.
“While consolidating all data onto a single storage system in a car does raise concerns regarding redundancy, there could be measures to mitigate potential risks,” Grossi said. “One approach is to implement distributed namespaces or sectors within the storage device, which can enhance fault tolerance and data reliability. Moreover, current storage solutions offer flexibility in addressing diverse application-endurance requirements. By configuring the NAND endurance mode, ranging from TLC for read-intensive use cases to SLC for applications requiring high PE endurance, manufacturers can tailor the storage system to suit the application’s needs.”
“We should also consider that automotive storage systems are designed to meet ASIL-B standards, which are adequate for the Cockpit and ADAS domains,” Sanchez said. “However, they may not be sufficient for the most stringent ASIL levels—such as C and D— required for critical systems like brakes, steering, cruise control, or engine control.”
Overall, while Micron’s 4150AT SSD can meet virtually all requirements of modern and upcoming cars in terms of performance, capacity and capabilities, there are still some functions of vehicles that must feature even more stringent functional safety. Micron is currently sampling its 4150AT among automotive customers and the drive will likely be used in vehicles in the coming years.
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