Power Loss Protection is yet another technology that Transcend employs to safeguard data integrity during a sudden power failure.
What is Power Loss Protection?
Power Loss Protection (PLP) is a Transcend technology for solid state drives (SSDs) with a DRAM cache that ensures the integrity of data in the event of a sudden power outage. PLP makes use of capacitors to prolong the time available to shift data in the DRAM cache to the SSD’s permanent flash memory. This ensures data integrity in the event of a power outage. During normal computer operations, these capacitors are charged so that they may power the SSD during an outage, ensuring that write operations are completed. By adding capacitors, PLP prolongs the time to complete the flushing of the DRAM cache to the permanent NAND memory after a sudden power loss.
How does PLP work?
Each SSD has a voltage detector that is constantly monitoring the voltage level coming from the host. Let's take the SSD452P for example. In the case of sudden power loss, the voltage detector triggers PLP as soon as the voltage drops from 5V to 4V. At this stage, PLP ensures that data stored in NAND remains intact. The built-in capacitors continue to provide power so that data can be flushed from DRAM into NAND. When the voltage drops below 2.6V, the NAND flash enters write-protection mode, and no more data is written.
Power failure with and without PLP
By prolonging the time between sudden power loss and the write protection mode, the SSD can complete more writes from the DRAM cache to the NAND flash.
To ensure dependability, Transcend puts its PLP technology through the Ulink DriveMaster power hub for testing. Each cycle consists of the following steps:
- Host issues write command to the controller.
- Controller writes data to the DRAM cache.
- Ulink powers off the host. When the VDT detects that the voltage drops to 4V, the data flushes from the DRAM cache to NAND flash.
- Ulink powers on the host and compares the data in the host with that on the NAND flash. If there is inconsistency in the data, the report shows a “miscompare” report.
Transcend’s PLP is put through 3,000 such testing cycles until no error messages are shown.
Advantages of Transcend’s PLP & PS
For top performance, Transcend uses superior components in PLP technology, such as an advanced voltage detector, to trigger PLP. Additionally, Transcend utilizes polymer tantalum capacitors – heavy-duty, low-profile capacitors that operate stably in harsh environments. Though an entry-level feature that requires no added capacitors, the Power Shield (PS) similarly enables the SSD’s internal power detecting mechanism to monitor power provided by the host. When the power fails, the voltage drops, and the voltage detector triggers the PS, which makes the SSD controller stop writing data to the NAND flash. This ensures that the data stored on the NAND is intact. However, unlike PLP, PS doesn’t create extra buffer time for the NAND flash to complete the write process.
Summary
PLP ensures data transfer integrity and minimizes the possibility of device failure during unexpected power outages on Transcend’s SSD products. To learn more about Power Shield (PS), please click here.