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As far as I know, there was no TRIM/UNMAP support in Windows before 7 (special tools were used for SSD drives), but flash drives were used since ~ 2005 and were fully supported by WindowsXP.

As USB Mass Storage Class devices they were using SCSI protocol on the top of USB (am I right at this point?). There is UNMAP is SCSI, but it was not supported in WinXP as well.

So, the only chance for USB Flash drive to know some block may be deleted is write request from OS.

That means after some usage whole drive is dirty and it is always slow. There is no way to tell it to delete any block. You only need to throw it away and buy new.

But I am sure that is not how it was. What did I miss?

  • TRIM doesn't effect nor is it used on flash drives even on OSs that support it. The reason that is the case is that TRIM isn't used on removable drives. – Ramhound Jan 29 '17 at 23:15
  • @Ramhound so when does flash drive delete blocks? UNMAP is supported on USB Attached SCSI, but only on USB 3.0 and Windows 8 – user996142 Jan 29 '17 at 23:17
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    I would have to research that topic before I answered your question. The only thing I do know is TRIM is not applicable to removal flash devices. – Ramhound Jan 29 '17 at 23:21
  • "It is confirmed that with native Microsoft drivers the TRIM command works on Windows 7 in AHCI and legacy IDE / ATA Mode. Windows 8 and later Windows operating systems support trim for PCI Express SSDs based on NVMe, and the unmap command which is a full analog of the TRIM command from Serial ATA for devices that use the SCSI driver stack." The NVMe, SATA via AHCI and IDE/ATA Mode are the only devices that support TRIM. – Ramhound Jan 29 '17 at 23:25
  • The Mass Storage Device used by USB devices does not support TRIM. The flash memory used in these devices are nothing like the flash memory in SSDs. – Ramhound Jan 29 '17 at 23:26

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