By PURPLELEC | 01 November 2023 | 0 Comments
How to prevent BGA SSD data loss
When a controlled SSD shutdown occurs, the ATA "standby immediately" command prompts the controller, allowing it to write all data in the buffer to the non-volatile NAND cells. In the event of a sudden voltage drop, if the host cannot send the "standby now" command to the controller, all unwritten information will be lost, resulting in file corruption. Therefore, the first protection level must replace the missing "early warning" of the host.
Level 1: Pressure drop detection
By monitoring the operating voltage, the BGA SSD controller can detect voltage drops in the event of a power failure. The controller's firmware can trigger two measures based on various thresholds: shutting down all operations and signaling Flash Write Protect (FWP). If the first threshold is reached, communication with the host is disabled, but the process of writing data to the SSD continues. If the second threshold is reached, writing is disabled to prevent corruption of saved data due to partial flash programming.
Level 2: Voltage margin
The second failure mechanism is related to voltage drop. Typically, the host voltage and flash voltage curves are parallel to each other. The task here is to get enough time for the SSD voltage drop curve to flatten.
The solution is to integrate capacitors into the BGA SSD power supply. Upon detection of the first threshold, the controller disables host operation and simultaneously discharges the capacitor to provide sufficient power to complete the write process. Weigu BGA SSD can provide such power failure protection function.
Level 3: Complete data backup
BGA SSD uses DRAM memory to improve performance and reduce write amplification factor (WAF). The level of the power-down mechanism described above leaves the DRAM memory data unprotected. If this data needs to be reliably written to flash memory during a power failure (a mechanism known as data hardening), more complex circuitry and larger capacitors' power reserves are required.
Power outage circuit
Highly durable capacitor banks can be integrated into a special power failure circuit with a power manager chip controlling the power supply. Under normal operating conditions, the chip receives power generated by the host to power the BGA SSD while charging the capacitor bank to a higher voltage. If a voltage drop is detected, the power manager chip switches power from the host to the capacitor. At the same time, it generates a power outage signal that triggers the controller's data hardening sequence. After the SSD writing process is completed, a "hardening complete" signal is generated to control the shutdown of the solid-state voltage source.
In addition to the state-of-the-art data loss protection mechanisms provided by BGA SSDs in the event of a power failure, these devices offer other features that differentiate them from server and even consumer-grade SSDs. These features include a sturdier housing and high-quality contacts. Another important feature of storage solutions for embedded applications is their long life.
This feature not only means long-term availability or deliverability of BGA SSDs, but from a technical perspective it is great investment protection while also improving durability. This characteristic is due to the many measures taken to prevent premature aging, such as lower write amplification factor (WAF) and over-provisioning.
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