FORTASA BLOG

Write Amplification is a major contributor to the reduced life expectancy of an SSD. Unlike a conventional HDD, Flash based SSD can’t simply write new user data on top of the previously recorded data. Instead, flash memory requires an erase and subsequently a re-write cycle to be issued to program the new information. Typically when the system needs to only update a single page of data, the flash controller has to read the full erase block size of data into the read buffer, update the desired page in the read buffer, erase the original block and re-write the updated block of data back to the Flash media. The same update process needs to occur not only to the data information itself, but also to the file table structure that links the data pages into a full information file. Therefore, a single page of data update actually mandates multiple Flash media writes. This process is commonly called – Write Amplification phenomenon.

Considering that Flash Media has a finite number of program/erase cycles as specified by the component Flash supplier, the SSD-wide Write Amplification phenomenon of increasing the number of program/erase cycles, significantly reduces the useful life of the SSD. Additional system requirement of Wear Leveling to spread the Flash Media usage by re-writing between static and dynamic data adds to the Write Amplification factor.

Many Flash controllers have tuned their algorithms to optimize the media interface and reduce the number of overhead writes for each page of data updates. Multiple innovations and patents have been developed and granted around efficient algorithms to reduce the Write Amplification overhead. An SSD manufacturer can empirically test, measure and compare the Write Amplification factor under a specifically defined test criteria. A test engineer would to record the number of data write command issued to the SSD and then compare to real flash memory program cycles as recorded by the Flash Controller (see SMART operation).

The Write Amplification factor can then be calculated by the following formula:

SSD Write Amplification Factor Calculation Formula

The measured Write Amplification factor can then be used in determining useful and reliable life for the SSD under similar usage conditions. Fortasa Memory Systems, Inc. performs Write Amplification and Product Life measurement for every device as part of our production release process.

Please contact Fortasa for specific Write Amplification / Lifecycle Calculation for any product we manufacture.