What is Active Garbage Collection for SSDs?

Active Garbage Collection, along with Trim, works to keep your solid state drive well-organized and ready for new data. As you use your drive, changing and deleting information, the SSD needs to make sure that invalid information is deleted from the drive and that there is available space for new information to be written.

How Active Garbage Collection works

Flash memory, which is what SSDs are made of, cannot overwrite existing data the way a hard disk drive can. Instead, solid state drives need to erase the now invalid data. The problem is that a larger unit of the memory, a block, must be erased before a smaller unit, a page, can be written. For example, if there are four pages with data in an otherwise empty block and three pages of data are deleted, the remaining page of data must be written to a new block, then all four pages in the old block can be deleted, freeing them up to be rewritten in the future.

If the drive were to not go through this process of moving valid information so that invalid information can be deleted, and instead, just keep writing new information to new pages, eventually it would fill up with data, some of it no longer valid. To prevent this, Active Garbage collection goes through the disk and moves each page of valid data to a page in another block so the block with invalid data, which has been identified with Trim, can be cleaned out.

Garbage collection and Trim work with wear leveling, an algorithm that ensures that each cell is written to and deleted from about the same number of times as all the other cells. This extends the life of the solid state drive.

Crucial SSD family

Active Garbage Collection support

Garbage collection occurs automatically using proprietary Active Garbage Collection functionality created by the manufacturer of the solid state drive. Because garbage collection is so important to the functioning of the drive, all drives have it.

Micron makes all of its solid state drives from the silicon up, and garbage collection is a vital part of the drive. Learn more about the process to manufacture SSDs.


Active garbage collection is an important part of the smooth functioning of an SSD. It works to move pieces of data around to allow more efficient and organized writing of new information and to streamline the deletion of invalid information.

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