Trim and Garbage-Collection
Garbage collection is a vital process in solid-state drives (SSDs) that ensures efficient data management and optimal storage space utilization. In SSDs, data is stored in units called pages, and multiple pages are grouped together to form a block. When data is deleted or marked as invalid, the SSD’s controller performs the garbage collection process to reclaim the space occupied by these invalidated pages. During garbage collection, the controller identifies blocks containing invalid data, gathers valid data pages, and relocates them to new empty blocks. Once the valid data has been moved, the old block with invalid data can be erased and made available for storing new data. Garbage collection is typically executed as a background operation during idle times or low activity to minimize disruption to regular data access.
TRIM is a feature that complements the garbage collection process in SSDs. It enables the operating system to proactively notify the SSD about which data pages are no longer needed or marked as invalid. When a user deletes or modifies data, the OS sends a TRIM command to the SSD, indicating the pages containing invalidated data.
TRIM and garbage collection
Without TRIM, the SSD’s controller may not immediately know which specific data pages are no longer needed or invalidated by the OS. This would require the garbage collection process to scan through all the data pages in a block during each cycle, including the invalid ones, to determine which ones are valid and which ones are not. As a result, unnecessary data copying and write operations may occur during garbage collection, leading to increased write amplification and reduced performance.
TRIM support, the OS can send a specific command to the SSD, indicating which data pages are invalid and can be safely erased. This allows the SSD’s controller to skip over the invalid data during garbage collection, reducing the need for extensive scanning and data movement. As a result, the garbage collection process becomes more efficient, leading to improved overall SSD performance and longevity. TRIM helps to streamline the garbage collection process and ensures that only valid data is moved to new blocks, while the invalid data is left behind to be erased later, reducing unnecessary write operations and wear on the SSD.
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