TRIM Command Support for WD External Drives


TRIM Command Support for WD External Drives


WD external SSD drives and WD external HDD drives that have SMR (Shingled Magnetic Recording) drive inside, offer TRIM command support which is enabled by default in Windows 7 and above, designed to maintain the performance of SSD or HDD at an optimal level over the lifetime of the drive. The TRIM command enables an OS (Operating System) to inform an SSD or HDD which blocks of data are no longer considered to be in use and can be reclaimed internally by the SSD or HDD to ensure that later write operations perform at full speed.


TRIM command support on the USB (SCSI) side is called UNMAP and the controller performs an UNMAP to TRIM translation. It maintains the performance at an optimal level (as fresh out of the box) over its lifetime and reduces the wear and tear of the drive, as it reclaims the occupied garbage space in advanced, avoiding unnecessary read-modify-write operations.


TRIM/UNMAP is supported for external hard drives with SMR (Shingled Magnetic Recording) drive inside, like SSDs, for dataset management and to improve SMR performance over time. One of the shingled write benefits is that all physical sectors are written sequentially in a direction radially and are only rewritten after a wrap-around. Rewriting a previously written LBA (Logical Block Addressing) will cause the previous write to be marked invalid and the LBA will be written to the next sequential physical sector. The TRIM/UNMAP enables the OS to inform the drive which blocks are no longer considered to be in use and can be reclaimed internally by the HDD to ensure that later write operations perform at full speed.


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