SSDs: Collecting Garbage and Being TRIM

StrorFly-TRIMFlash memory consists of blocks and pages within those blocks. An SSD can write pages to empty blocks quickly, but when an erase command is issued, it has to erase an entire block before it can write new pages to it. Data to be retained must be moved to an open block before the original block can be entirely flushed and that space reclaimed. This process, built into SSDs, is called Garbage Collection (GC).

While an SSD effectively does GC, operating systems can’t tell what blocks are free until the erase operation starts. This and continued read/erase/write operation slow down and wear out an SSD.

Enter TRIM. First off, TRIM is not an acronym and appears as both Trim and TRIM. TRIM is a command built into newer operating systems that enables you to know beforehand which blocks of data are no longer wanted and can be wiped.

The advantage of the TRIM command is that it enables an SSD’s GC function to skip the unwanted data rather than moving it, thus saving time not rewriting the invalid data. The SSD doesn’t need to immediately delete or garbage collect these locations it just marks them as no longer valid. So in a way the space used on the SSD is being “trimmed” – ah ha!

The result is a reduction of flash memory erase cycles, enabling higher performance during writes and less wear and tear on the drive.

There are a several other ways to increase the performance and endurance of your SSD – and the main one of course, is to start out with a high-quality industrial-grade SSD like those from Virtium’s StorFly® family.