Interface Analysis: SATA, PCIe, and NVMe
Choosing the appropriate component requires careful consideration of both the storage medium and the interface that links it to the host system. The interface often serves as the primary limiting factor in realizing the full speed potential of the NAND.
As your engineering collaborator, the Suntsu team offers the technical support needed to ensure your PCB design effectively integrates the M.2 connector and chooses the appropriate drive keying for your selected interface.
NAND Flash Deep Dive: SLC, MLC, TLC, and QLC
The core component of the SSD is the NAND Flash Memory. Its design plays a crucial role in determining the drive’s cost, speed, and most importantly, its endurance, which is measured in Program/Erase (P/E) cycles.
The differences lie in how many data bits are stored per memory cell:
Selection Criteria: Endurance vs. Cost
Choosing the right SSD means weighing Total Bytes Written (TBW) requirements against budget. Engineers should evaluate the full system workload and forecast lifetime writes, then match that to the NAND type most suitable for the application.
For example:
- A ruggedized industrial controller may require SLC or industrial-grade MLC SSDs.
- A laptop fleet can balance performance and cost with TLC SSDs.
- A data center focused on cold storage might adopt QLC SSDs for maximum capacity per dollar.
How Suntsu Can Help
In some cases, off-the-shelf SSDs may not meet the endurance, temperature, or compliance requirements of industrial designs. Suntsu’s Engineering Services can assist with:
- Component Engineering: Identifying industrial-grade NAND ICs from suppliers such as Jeju Semiconductor Corporation (JSC).
- Custom/Industrial SSDs: Partnering with specialized SSD makers like Flexxon to provide secure, high-reliability storage solutions tailored for unique use cases.
- Longevity Risk Mitigation: Advising on parts with stable roadmaps and long-term availability to prevent redesigns.
By proactively aligning NAND technology with system endurance and cost goals, engineers can select the right SSD solution while safeguarding long-term reliability.
Connect with our expert engineering team to secure the high-performance SSDs your design demands, and let us help you overcome component sourcing challenges today.
FAQs
Wear-leveling and garbage collection are the two core technical functions performed by the SSD controller to maximize the drive’s endurance and maintain performance:
- Wear-Leveling: This is a technique used to evenly distribute Program/Erase (P/E) cycles across all NAND blocks in the drive. Since a flash cell can only endure a finite number of writes (e.g., 3,000 for TLC), the controller ensures frequently written data is not always mapped to the same physical blocks. It uses the Flash Translation Layer (FTL), which acts as a logical-to-physical address map, to constantly move data and spread the wear, preventing any single block from prematurely failing.
- Garbage Collection: NAND flash cannot overwrite existing data; it can only write to empty pages within blocks. To “erase” data, the entire block must be erased, a process that is slow. Garbage collection is the controller’s background process that identifies blocks containing both valid (still needed) and invalid (deleted) pages. It reads the valid data pages, writes them to a new, empty block, and then erases the old block entirely, making it available for new data. This process is essential for maintaining a pool of fresh, empty blocks to ensure fast write performance.
Both metrics define the expected lifespan of an SSD, but they are used for different engineering analyses:
- TBW (Total Bytes Written): This is the cumulative amount of data (in terabytes) that is guaranteed to be written to the SSD over its warrantied life. It’s an absolute number, perfect for planning a system with a fixed, finite life cycle or a known amount of total data logging required.
- Example: If an industrial controller will log 10TB of data over a 5-year project life, you need an SSD with a TBW rating of at least 10TB.
- DWPD (Drive Writes Per Day): This is the number of times the total capacity of the drive can be overwritten each day for the duration of the warranty (typically 3 or 5 years). It’s a rate, ideal for calculating endurance for always-on, enterprise, or high-duty-cycle industrial systems.
- Calculation:
- A drive with a 1 DWPD rating means you can write the equivalent of the entire drive’s capacity once per day for the warranty period.
Yes, the failure modes for SSDs are fundamentally different from HDDs, which is crucial for preventative system design:
- HDD Failure Mode: HDDs typically exhibit mechanical failures, such as a head crash, motor failure, or bearing seizure. These failures often result in a sudden, catastrophic loss of access to data, but the data on the platters may sometimes be recoverable by specialists.
- SSD Failure Modes: SSDs primarily experience controller failures or NAND wear-out.
- Wear-Out: As blocks reach their P/E cycle limit, they become “read-only” to prevent data corruption. A well-managed SSD will transition to a read-only state upon reaching the end of its life, meaning the existing data remains accessible, but no new data can be written.
- Controller/Firmware Failure: This is a less common but more catastrophic failure where the controller chip or its firmware malfunctions. The drive may stop responding, or the FTL may become corrupted, making the drive inaccessible.
Power Loss Protection (PLP) is a critical feature that differentiates consumer-grade from industrial-grade and enterprise SSDs:
- Function: PLP utilizes on-board capacitors (not batteries) to store a small reserve of electrical energy. In the event of an unexpected power interruption (such as a sudden shutdown or brownout), this reserve power is used to provide the SSD controller with enough time (typically a few milliseconds) to complete any write operations currently held in the DRAM cache and commit the critical FTL mapping tables to the NAND.
- Essential for Industrial Use: In industrial, medical, and high-reliability embedded systems, the integrity of the data and the FTL map is paramount. Without PLP, an unexpected power loss can lead to data corruption or, worse, a corrupted FTL map that renders the entire drive unusable, causing costly downtime and system failure. Always verify that industrial-grade SSDs are rated for full data path protection (protecting both user data and mapping tables).
Over-provisioning (OP) is a technique used to reserve a portion of the SSD’s total NAND capacity for controller use, which is essential for maximizing endurance and performance in write-intensive applications:
- Function: The reserved space is not visible to the operating system; it is used solely by the controller for wear-leveling, garbage collection, and managing replacement blocks. By increasing the pool of available blocks, the controller can execute garbage collection more efficiently and spread write activity over a larger area, reducing the Write Amplification Factor (WAF).
- Optimal Ratio Calculation: The OP ratio depends heavily on the workload.
- Standard SSDs typically have a baseline OP of about 7% (e.g., a 128GB drive marketed as 120GB).
- Write-Intensive Workloads (e.g., constant logging): Engineers should consider 28% OP (e.g., a 512GB drive marketed as 400GB) or even 40%+ for heavy-duty industrial logging. This calculation involves estimating the peak WAF and ensuring the available spare block ratio is sufficient to maintain the target DWPD. Consulting a component engineer is highly recommended for optimizing the OP ratio to match your specific application profile.
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