如果你的3.0U盘支持的是 BOT mode，那么很可能传输速度较慢。
判断的方法是查看描述符中的 Interface Protocol，如果是50h，那么就是。比如，下面来自我手上的一个U盘：
[Port13] : USB Mass Storage Device
Is Port User Connectable: yes
Is Port Debug Capable: yes
Companion Port Number: 3
Companion Hub Symbolic Link Name: USB#ROOT_HUB30#4&16cc2fc5&0&0#{f18a0e88-c30c-11d0-8815-00a0c906bed8}
Protocols Supported:
USB 1.1: no
USB 2.0: no
USB 3.0: yes
Device Power State: PowerDeviceD0
---===>Device Information<===---
English product name: "Disk 20"
ConnectionStatus:
Current Config Value: 0x01 -> Device Bus Speed: SuperSpeed
Device Address: 0x17
Open Pipes: 2
===>Device Descriptor<===
bLength: 0x12
bDescriptorType: 0x01
bcdUSB: 0x0320
bDeviceClass: 0x00 -> This is an Interface Class Defined Device
bDeviceSubClass: 0x00
bDeviceProtocol: 0x00
bMaxPacketSize0: 0x09 = (9) Bytes
idVendor: 0x346D = Vendor ID not listed with USB.org
idProduct: 0x5678
bcdDevice: 0x0200
iManufacturer: 0x01
English (United States) "USB"
iProduct: 0x02
English (United States) "Disk 20"
iSerialNumber: 0x03
English (United States) "FC097CCF38A2A"
bNumConfigurations: 0x01
---===>Open Pipes<===---
===>Endpoint Descriptor<===
bLength: 0x07
bDescriptorType: 0x05
bEndpointAddress: 0x01 -> Direction: OUT - EndpointID: 1
bmAttributes: 0x02 -> Bulk Transfer Type
wMaxPacketSize: 0x0400
bInterval: 0x00
===>Endpoint Descriptor<===
bLength: 0x07
bDescriptorType: 0x05
bEndpointAddress: 0x81 -> Direction: IN - EndpointID: 1
bmAttributes: 0x02 -> Bulk Transfer Type
wMaxPacketSize: 0x0400
bInterval: 0x00
---===>Full Configuration Descriptor<===---
===>Configuration Descriptor<===
bLength: 0x09
bDescriptorType: 0x02
wTotalLength: 0x002C -> Validated
bNumInterfaces: 0x01
bConfigurationValue: 0x01
iConfiguration: 0x00
bmAttributes: 0x80 -> Bus Powered
MaxPower: 0x12 = 144 mA
===>Interface Descriptor<===
bLength: 0x09
bDescriptorType: 0x04
bInterfaceNumber: 0x00
bAlternateSetting: 0x00
bNumEndpoints: 0x02
bInterfaceClass: 0x08 -> This is a Mass Storage USB Device Interface Class
bInterfaceSubClass: 0x06
bInterfaceProtocol: 0x50
iInterface: 0x00
如果使用抓包工具，会看到下面这种模式的传输
31B OUT
大块 IN
13B IN
与之相反，还有一种UASP，对应的Interface Protocol 是 62h，速度更快。