Endurance, Latency, and Workload Considerations for Choosing Dashcam Memory Cards (Part 1)

As the resolution and development of dashcam or DVR evolve, merely looking for high-capacity storage is not enough. To record videos non-stop for thousands of hours without compromising data integrity, you will need high-endurance Memory Cards.

Challenges for dashcam storage

Recording Challenges

• Non-Stop Operation. Dashcams/DVRs typically operate for extended periods of time. Recording over and over again may cause NAND storage failure on video.

• Latency Under Different Temperature Profiles. Both extreme heat and cold environments can affect flash memory cells and the performance of the storage media.

• Harsh Operating Conditions. Environmental conditions of camera location contribute to flash degradation and can endanger the integrity of the data in it.

• Power Supply Instability. Any power flux or interruption may cause damage to the dashcam or storage device, thus corrupting data integrity.

What should we consider when choosing a memory card for recording?

1. Endurance Matters

The endless writing/rewriting of camera recording causes NAND flash cells on the storage media to wear out, leading to possible video corruption and rendering the stored data useless when it is needed most.

NAND P/E cycles may have a direct impact on storage lifetime. With different NAND architectures, endurance could have 2-3 times extension.

Evenly distributing erase counts to each block could extend the lifetime of the storage device on the recording media.

Endurance = Recording Hours = Capacity?

As demand for longer recording time increases, unsurprisingly, more and more high-capacity memory cards are successively being launched to fulfill the demands of the dashcam market. For example, when recording a 4K video (100Mbps), a 256GB memory card can store about 5 hours and 40 minutes before it is full and overwritten for a new recording.

Users may choose a super high-capacity memory card just for longer recording time but as usage time increases and with the non-stop writing and rewriting day by day on storage devices, a high-endurance memory card with a suitable warranty is the one that stands out and provides higher recording quality as well as better data integrity for long-term recording time.  

Figure 1. Continuous recording hours with 128 GB memory card

Notes:

• Tested using 128GB ATP S650 TLC card based on 13Mbps (lowest bitrate of HD recording) in the best-case/ideal scenario, with no other influencing factors.

• Information sourced by ATP from publicly available data.

• To record new data, the oldest data will be overwritten when the card is full.

• 1Mbps=1,000,000bps

Table 1. Estimated non-stop recording hours with ATP high-endurance card

2. Low Latency: Fast Response is Critical

Users expect their systems to be ready with fast response for evidence recording. Taking the drive recorder as an example — after power on, the bootup time depends on the embedded memory, yet the time required to be ready for recording and succeeding programming depends on the external/removable storage, such as SD/microSD cards.

Figure 2: Drive recorder response time

High-endurance memory cards built for dashcam recording may save more than 50% time to be ready for recording than other commercial cards under different environmental conditions, which can effectively help the critical video being recorded.

Table 2: Maximum response time(s): fast response in any temperature scenario

 Figure 3. It only takes 2.25 seconds to respond to the host and prepare for recording @-20^oC

Notes:

The point represents 1 cycle within DVR: 2 mins. power on and 2 mins. power off.

The complete test duration is around 18 hours. We collect the latest 250 points (dirty state).

3. Workload Matters

To understand the lifetime and quality of the recording, information from the host and memory storage may be a key indicator.

ATP SD Life Monitor tool can be applied for product development.

• Workload Inspection. On Windows, the ATP SD Life Monitor tool provides health status reports and card identification information. Furthermore, with an additional "Workload Inspection" pie chart, users can quickly check the write operation and file size by the host systems.

Considering the NAND flash page size and FW algorithm, ATP provides recommendations and more information for the host devices' program data based on the multiples of minimum data transfer size in the SD/microSD card datasheet. 

Figure 4. ATP SD Life Monitor illustrates the example that the majority of file sizes written by the host device is 64 KB (121 times).

ATP Joint Validation Service with host workload inspection can provide customers comprehensive solutions on both hardware and software concerns. 

• On Linux, customers can install the ATP SD Guardian tool that has a user-friendly interface for information display or refer to the ATP Command 56 guidelines, which can directly issue SD vendor commands for software integration. 

ATP Electronics recently introduced its new 3D triple-level cell (TLC) S750/S650 Series High-Endurance SD and microSD memory cards built for continuous video recording. They meet the high endurance, low latency, and built-to-last data storage requirements of dashcams and digital video recorders (DVRs), as well as surveillance systems, autonomous vehicles, and other write-intensive applications.