This is known as “overprovisioning” - extra storage hardware is added to the drive but isn’t visible to the computer as available storage it can use. To prevent consumers from filling up their solid-state drives and ending up with severely degraded performance, SSD manufacturers are going out of their way to counter this.Ĭonsumer-grade solid-state drives often set aside about 7% of their total flash storage and make it unavailable to the user.
#LAPTOP RUNNING SLOWLY AFTER DROP FULL#
The drive will still be full of partially filled blocks and write performance will be degraded. The drive won’t go out of its way to consolidate these partially-filled blocks into full blocks, freeing up empty blocks. In other words, fill a solid-state drive to capacity before deleting files and you’ll likely end up with many partially filled blocks. It doesn’t force the drive to do any sort of cleanup operation. The TRIM command just directs a solid-state drive to remove file data when the file is deleted. If you fill a drive to capacity or near capacity, it’s likely that you’ll end up with many partially filled blocks after you delete files. TRIM Doesn’t Consolidate Partially Filled Blocks Bear in mind that writing a file will likely involve writing to many blocks, so this can introduce a significant amount of additional delay. Instead of a simple write operation, the solid-state drive has to read the value of the block into its cache, modify the value with the new data, and then write it back. The solid-state drive can’t just write the new data to these partially filled blocks - that would erase the existing data.
In their place are partially filled blocks. To add additional pages to a partially filled block, the solid-state drive must erase the entire block before writing data back to it.Īs your solid-state drive fills up, fewer and fewer empty blocks are available.
NAND Flash memory writes data in 4 KB pages inside of 256 KB blocks. Writing over an already-written sector is just as fast as writing to an empty sector on a mechnical hard drive, but a solid-state drive must erase a block before writing to it. They don’t sit around on a solid-state drive - TRIM ensures that the block is emptied so the SSD can quickly write new data to the empty block in the future. This works differently from magnetic hard drives, where bits of deleted files sit around on the hard drive.
That’s why new operating systems (Windows 7 and later) support the TRIM feature, which automatically deletes a file’s data from the solid-state drive as soon as you delete the file in your operating system. Writing to an empty block is the fastest possible write operation. When you write a file to your solid-state drive, it looks for empty blocks and fills them.