Estimation method for data access performance

An estimation method for data access performance, which is applied in a computer system having a host and a flash memory device, the flash memory device comprising a controller and a flash memory module, the flash memory module comprising a plurality of blocks that includes at least one free block with no data stored, steps of the estimation method comprising:

• transmitting a writing performance query instruction, which indicates the amount of data to be written, to the flash memory device via the host;
• and
• demanding the controller of the flash memory device to execute a writing performance estimation process after receiving the writing performance query instruction, steps of the writing performance estimation process comprising:
• determining whether data space of the free block is sufficient to accommodate the amount of data to be written, if so, transmitting a reply signal indicating an optimal writing performance to the host, if not, executing a garbage collection process;
• steps of the garbage collection process comprising:
• selecting at least one the block, from these blocks with data stored, to be executed the garbage collection process;
• determining the amount of valid data within the selected block;
• calculating a weight ratio based on the amount of valid data within the selected block divided by the sum of the amount of valid data within the selected block and the amount of data to be written;
• subtracting the weight ratio from the optimal writing performance to obtain an estimated writing performance;
• transmitting a reply signal indicating the estimated writing performance to the host;
• and
• executing the garbage collection for the selected block to move the valid data in the selected block into other blocks and erase all data in the selected block such that the selected block becomes the new free block.