We know that TRIM feature is available on SSDs to improve it’s performance. But why it’s on a hard drive?
What TRIM command does is, it allows OS to tell the SSD that which blocks are no more needed and can be wiped out. Because SSD or any other NAND flashes have to delete the data on blocks before overwriting them. Basically
TRIM wipes the data in background you deleted beforehand, so you can write on that blocks of SSD with full speed.
But in HDD, if it’s a SMR or Shingled Magnetic Recording Drive, then engineers include the feature TRIM. SMR drives are way slower than your usual CMR drive, so to improve performance the feature has to be included.
But HDDs doesn’t need to erase the blocks before overwriting, so with TRIM command it renders the previous used blocks as not in use (The files you have deleted before), so it can write with full speed without doing background work as TRIM enabled SSDs.
TRIM basically works very differently between HDD and SSDs.