Everything you need to know about SSD Latency

Latency refers to the total time delay between the user’s action and the response from the system. In the context of SSD, when the data is being read from or written to the drive, the latency determines how fast the data will be processed in the required manner.

We have talked about SSD latency in this article as well. There, we understood that:

Latency refers to the time delay experienced in a system, specifically the time it takes for a specific block of data to travel from one point to another. In the context of storage systems and networks, latency is often measured in milliseconds (ms) and represents the delay between issuing a command and receiving a response. It’s a crucial metric for understanding the responsiveness of any system that involves data transfer or communication.

Not only the data read/write requests, but latency can also play a big role in the overall performance of your system. As the drive gets faster, the latency gets lower and lower hence reducing the time it takes for the data requests to go here and there. So, there is a direct link between the drive performance and latency. Let’s talk a little more about it and see how you can reduce the SSD latency.

Understanding SSD Latency

To provide a clearer picture: imagine sending a command to your SSD and waiting for a mere 0.05 milliseconds (ms) before it responds. That’s the kind of latency we can expect from high-end SSDs. In contrast, traditional HDDs might exhibit latencies of around 5-10ms—a staggering 100 to 200 times slower.

Contrast this with throughput, a term often flaunted in tech specifications. If throughput represents the highway’s width (indicating how many cars or, in this case, bits of data can travel side by side), latency is the time it takes for the first car to reach its destination. For instance, an SSD might boast a throughput of 500 megabytes per second (MB/s), meaning it can process 500 MB of data every second. But if its latency is high, you might have to wait a discernible amount of time before that data transfer begins.

In numerical terms, reducing SSD latency from 0.1ms to 0.05ms could result in a perceptible 50% improvement in response times for certain tasks, even if the throughput remains unchanged. Hence, while throughput paints a picture of the SSD’s overall capacity to handle data, latency gives insights into its immediacy and reactivity—crucial for tasks demanding instant data access.

Factors that influence SSD latency:

1. NAND Type: The kind of NAND flash memory used in the SSD plays a role. For instance, Single-Level Cell (SLC) NAND generally offers lower latency compared to Multi-Level Cell (MLC) or Triple-Level Cell (TLC) NAND.

2. Controller Efficiency: The SSD’s controller, which manages data storage and retrieval, can impact latency. A more efficient controller can swiftly address and manage data requests, thus reducing latency.
3. Parallelism: Modern SSDs employ multiple NAND flash memory chips and can access them concurrently. This parallel access can help in reducing the perceived latency, especially for large data requests.
4. Drive Wear: As an SSD undergoes more write and erase cycles, certain sections of the NAND memory can slow down, leading to increased latency.
5. External Factors: The interface used (like SATA or NVMe), the system’s motherboard, and even the operating system can play roles in determining the latency.

Types of Latencies in SSDs

End-User Influence vs. Manufacturer Dependence on SSD Latency

SSD latency, like most technical attributes of a hardware component, is shaped by a blend of inherent design choices and external optimization opportunities. But how much control does an end-user genuinely have over this metric, and to what extent is it preset by the manufacturer?

1. Inherent Design and Manufacturer Control:
   • NAND Quality and Type: The choice between SLC, MLC, TLC, or QLC NAND inherently determines the latency characteristics of the SSD. SLCs, with only one bit per cell, generally have the lowest latency. SLC is impractical for everyday usage because of its expensive price. Try to go at least for TLC SSD.
   • Controller Design: The efficiency of an SSD controller, its algorithms, and its ability to manage data access, wear leveling, and garbage collection significantly influence latency. This too is a design choice made by the manufacturer.
   • Parallelism and Channels: SSDs designed with multiple NAND channels that work in parallel can have lower latencies. Again, this design choice rests with the manufacturer.
   • Drive Architecture and Firmware: While firmware can be updated post-purchase, the fundamental architecture and initial firmware optimization are under the manufacturer’s domain.
2. End-User Influence:
   • Firmware Updates: Manufacturers occasionally release firmware updates that can optimize performance and potentially reduce latency. Keeping the SSD firmware up-to-date is within the user’s control.
   • Optimal Usage Practices: Over-provisioning, maintaining free space, and allowing idle time for garbage collection can aid in reducing latency.
   • System and Software Optimization: Choosing the right file system, tweaking OS settings, and using SSD-optimized software can influence the perceived latency.
   • Heat Management: SSD Thermal Throttling can cause a reduction in speed that indirectly impacts the latency as well. So, make sure to keep your SSD safe from external heat with the help of passive coolers.

While end-users can do some optimizations to enhance SSD performance and potentially reduce latency, most of the core determinants of SSD latency lie in the SSD components and manufacturing choices. As such, a substantial part of an SSD’s latency profile is set at the factory level. This underscores the importance of thorough research and selecting high-quality SSDs from reputable manufacturers. By investing in an SSD with low inherent latency, users are better positioned to reap the full benefits of any subsequent optimizations they implement.

How to reduce SSD Latency?

You can’t actually tweak any setting in your system or SSD to increase or decrease the latency. It surely is influenced by several external factors but after a point, you can hardly do anything to increase it. This basically comes down to the controller and NAND specifications of your drive. However, there are several things that you can do to reduce it as much as possible.

1. Over-Provisioning

Allocating more NAND capacity than is publicly available can be a game-changer. By keeping a portion of the SSD’s capacity unused, the controller has additional space to manage data efficiently. Resultantly, over-provisioning can reduce write amplification, leading to a latency improvement of up to 20% in certain SSDs.

• How to Implement: Most SSDs come with a certain amount of over-provisioning by default. However, you can increase this manually.
• Steps:
  1. Backup all data from your SSD.
  2. Using SSD management software (like Samsung Magician for Samsung SSDs), access the over-provisioning setting.
  3. Adjust the slider or input a specific percentage of the SSD to be over-provisioned.
  4. Apply the changes, which might format the drive, ensuring you have backups.

2. Garbage Collection

This process reclaims space from deleted or modified data to make room for new data. By optimizing garbage collection algorithms, SSDs can avoid unnecessary write and erase cycles, potentially cutting down latency by 15%.

• How to Implement: While garbage collection is an automatic internal process of SSDs, you can optimize its performance.
• Steps:
  1. Allow the SSD to remain powered on but idle; the drive will use this idle time to perform garbage collection.
  2. Refrain from filling the SSD to its maximum capacity; keeping some free space can enhance the efficiency of the garbage collection process.

3. Wear Leveling Optimization

Aiming for an even distribution of write/erase cycles across the NAND cells ensures that no single cell gets overused. Proper wear leveling can maintain consistent latency levels throughout the SSD’s lifespan, staving off latency spikes that can arise from uneven wear.

• How to Implement: Wear leveling is primarily managed by the SSD controller, but you can adopt practices that support its effectiveness.
• Steps:
  1. Ensure firmware is updated: Modern firmware versions have improved wear-leveling algorithms.
  2. Use SSDs that inherently support wear leveling. Check the product specifications or datasheet.
  3. Maintain a healthy amount of free space on your SSD, allowing the controller more room to evenly distribute write and erase cycles.

4. Up-to-Date Firmware

Firmware acts as the SSD’s operating system. By ensuring the firmware is current, users can benefit from the latest optimizations and bug fixes, which can improve latency by approximately 10% in specific scenarios.

• How to Implement: Keeping your SSD’s firmware updated ensures you benefit from the latest performance enhancements and bug fixes.
• Steps:
  1. Download the SSD manufacturer’s utility software (e.g., Crucial Storage Executive for Crucial SSDs, Samsung Magician for Samsung SSDs).
  2. Open the software and check for firmware updates.
  3. If an update is available, follow the prompts to install it.

5. Choosing the Right File System

Some file systems, like F2FS or EXT4, are tailored for SSDs. Utilizing these can lead to more efficient data storage and retrieval, cutting down latency times by up to 5%.

• How to Implement: Select a file system optimized for SSD performance.
• Steps:
  1. Backup your SSD data.
  2. Format the SSD using a preferred file system (like F2FS or EXT4 for Linux, APFS for macOS).
  3. Restore your data to the SSD.

6. Optimizing Operating System Settings

Adjusting certain SSD settings within the OS can lead to reduced latency. For instance, disabling automatic defragmentation on SSDs (a process more suited to HDDs) can result in latency improvements.

• How to Implement: Various OS settings can be tweaked to favor SSD performance.
• Steps for Windows:
  1. Open ‘System Properties’ > ‘Advanced’ > ‘Performance Settings’.
  2. Ensure ‘Automatically manage paging file size for all drives’ is checked.
  3. Disable ‘Disk Defragmentation’ for your SSD.
  4. Enable ‘Trim’ using the command fsutil behavior set DisableDeleteNotify 0.

7. Parallelism

As mentioned earlier, leveraging the concurrent access capabilities of modern SSDs can diminish perceived latency. By optimizing command queues and streamlining data requests, SSDs can achieve up to a 25% reduction in latency during heavy workloads.

• How to Implement: Ensure your SSD and motherboard support NVMe, which inherently takes advantage of parallelism.
• Steps:
  1. Install the SSD on an NVMe-compatible slot on your motherboard.
  2. Ensure drivers are updated to take full advantage of NVMe features.

As we discussed earlier, most of these things are automatically happening inside your solid-state drive. However, you can make sure to keep the drivers/firmware updates and all the important settings turned On to make sure nothing is increasing the SSD latency indirectly.

Importance of SSD Quality and Make in Latency

While the strategies to reduce latency are essential, the inherent quality and construction of the SSD itself play a pivotal role in its performance metrics.

1. NAND Quality: An SSD equipped with premium Single-Level Cell (SLC) NAND, for instance, will inherently possess lower latency compared to those with Multi-Level Cell (MLC) or Triple-Level Cell (TLC) NAND. In certain benchmark tests, premium SLC NANDs exhibited up to 30% lower latency than their MLC counterparts.
2. Controller Capabilities: The controller is the heart of an SSD, doing everything from data storage to retrieval. High-end SSDs often come with advanced controllers that handle tasks more efficiently. For instance, SSDs with a state-of-the-art NVMe controller might showcase up to 40% lower latency compared to older AHCI-based SATA SSDs under similar conditions.
3. Manufacturing Precision: SSDs made with stringent quality controls will have fewer defects, ensuring consistent performance. Such drives can potentially exhibit up to 15% lower latency variations compared to those from less meticulous manufacturing processes. So, when choosing your SSD, make sure to go for the reputed brands.
4. Brand Reliability: Renowned SSD manufacturers often invest heavily in research and development, ensuring their products are optimized for performance. Choosing an SSD from a reputable brand can inherently assure lower latency. Research has shown that top-tier brands, on average, outperform lesser-known brands by approximately 20% in latency benchmarks.
5. Drive Architecture: Some SSDs are designed with a focus on parallelism, utilizing multiple NAND channels simultaneously. These drives, when compared to their single or dual-channel counterparts, can exhibit up to a 35% reduction in latency during data-intensive tasks.

In essence, while external optimizations are crucial, choosing an SSD with superior internal architecture and quality is half the battle won. Investing in a high-quality SSD from the outset ensures a foundation for minimal latency, leading to swift and efficient data access.

High Latency and its impacts on different computation tasks

Frequently Asked Questions