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I wonder if Pi 4 supports UASP (USB Attached SCSI Protocol). This may need everything from the VLI VL805-06 USB controller to the firmware to the driver to supp

by k_sze 7y ago

I wonder if Pi 4 supports UASP (USB Attached SCSI Protocol). This may need everything from the VLI VL805-06 USB controller to the firmware to the driver to support it. A preliminary DDG search suggests that the controller probably supports it. My understanding is that, if UASP is supported, you can squeeze even more performance out of a SSD, and it will even properly support the TRIM command because then the SSD is no longer just a dumb USB mass storage device.

geerlingguy 7y ago
This would be interesting to check; I know there are few people on the Pi forums exploring some of the outer edges of what's now possible with a decent USB controller.
bonzini 7y ago
TRIM is supported by USB mass storage devices since those are _also_ SCSI. It is the bridges that may not support it, and the same is true for USB-attached SCSI. For USB-attached SCSI, what makes a difference in performance is support for USB 3.0 streams, which allow multiple transfers to occur concurrently (https://www.kernel.org/doc/html/latest/driver-api/usb/bulk-streams.html https://www.kernel.org/doc/html/latest/driver-api/usb/bulk-s...).
- k_sze 7y ago
  Ah. I didn't know that USB mass storage is also SCSI. Is TRIM/UNMAP part of the SCSI Transparent Command Set, which depends on the SCSI Peripheral Device Type reported (by the USB-SATA bridge?) in response to INQUIRY? What exactly is the "SCSI Transparent Command Set" anyway? I haven't been able to find an answer from DuckDuckGo search. The Wikipedia article on USB Mass Storage [1] mentions it, but doesn't really define it. Neither does the article on the SCSI command [2] itself. Another post [3] touches upon SCSI Transparent Command Set, but also says in passing that the SCSI specifications at t10.org don't mention the "SCSI Transparent Command Set". [1] https://en.wikipedia.org/wiki/USB_mass_storage_device_class#Device_access https://en.wikipedia.org/wiki/USB_mass_storage_device_class#... [2] https://en.wikipedia.org/wiki/SCSI_command https://en.wikipedia.org/wiki/SCSI_command [3] http://janaxelson.com/mass_storage_faq.htm http://janaxelson.com/mass_storage_faq.htm

by k_sze 7y ago

geerlingguy 7y ago

This would be interesting to check; I know there are few people on the Pi forums exploring some of the outer edges of what's now possible with a decent USB controller.

bonzini 7y ago

TRIM is supported by USB mass storage devices since those are _also_ SCSI. It is the bridges that may not support it, and the same is true for USB-attached SCSI. For USB-attached SCSI, what makes a difference in performance is support for USB 3.0 streams, which allow multiple transfers to occur concurrently (https://www.kernel.org/doc/html/latest/driver-api/usb/bulk-streams.html https://www.kernel.org/doc/html/latest/driver-api/usb/bulk-s...).

k_sze 7y ago
Ah. I didn't know that USB mass storage is also SCSI. Is TRIM/UNMAP part of the SCSI Transparent Command Set, which depends on the SCSI Peripheral Device Type reported (by the USB-SATA bridge?) in response to INQUIRY? What exactly is the "SCSI Transparent Command Set" anyway? I haven't been able to find an answer from DuckDuckGo search. The Wikipedia article on USB Mass Storage [1] mentions it, but doesn't really define it. Neither does the article on the SCSI command [2] itself. Another post [3] touches upon SCSI Transparent Command Set, but also says in passing that the SCSI specifications at t10.org don't mention the "SCSI Transparent Command Set". [1] https://en.wikipedia.org/wiki/USB_mass_storage_device_class#Device_access https://en.wikipedia.org/wiki/USB_mass_storage_device_class#... [2] https://en.wikipedia.org/wiki/SCSI_command https://en.wikipedia.org/wiki/SCSI_command [3] http://janaxelson.com/mass_storage_faq.htm http://janaxelson.com/mass_storage_faq.htm