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USB mass storage device class (USB MSC) is a family of USB specifications that standardizes how a USB host communicates with storage. It is not a particular product or a filesystem: it describes the host-device interface, while separate specifications define how commands and data travel.
What does USB mass storage class mean?
A USB host—such as a computer—uses the mass storage class to communicate with a device that exposes storage. A familiar example is a USB flash drive. The host can see storage as a disk or, in some implementations, as a CD-ROM drive.
The class is a family of specifications rather than one single protocol. The USB-IF document library lists an overview along with related transport and command-set documents, including Bulk-Only Transport (BOT), CBI, UFI, and UASP-related material.
How is the class different from a transport?
The class describes the broader standardized storage interface; a transport specifies how commands, data, and status are carried between host and device. BOT is one such transport, not another name for every USB storage transport.
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- USB-C 2-in-1 storage OTG: The Lexar JumpDrive Dual Drive D40E features USB Type-A and Type-C connectors in a slim, portable form factor for easy device compatibility
- Transfer speeds up to 100MB/s: Based on internal testing, performance may vary depending upon the host device, interface, and usage conditions. 1MB=1,000,000 bytes
- Plug and Play: Widely compatible with USB Type-C smartphones, tablets, laptops, Macs, and traditional Type-A devices, no software installation required. The 360° swivel design allows for easy switching between connectors without the hassle of losing a cap
- Durable & Compact: The Lexar D40E USB memory stick features a metal enclosure, withstands temperatures from 0° to 50° C (32°F to 122°F), and is lightweight at 26g with dimensions of 70.4 x 16.9 x 11.7mm
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What is Bulk-Only Transport?
The USB-IF’s Bulk-Only Transport Revision 1.0 specification defines a method for transferring command, data, and status solely through bulk endpoints. It does not require an interrupt endpoint; specified control actions use the default pipe.
The USB-IF library lists BOT Revision 1.0 with a date of September 30, 1999. The document cover shows an invalid date, September 31, 1999, so the library listing date is used here. The library also lists a Mass Storage Class Specification Overview 1.4 dated February 19, 2010; CBI 1.1 dated June 23, 2003; UFI Command Specification 1.0 dated December 14, 1998; Mass Storage Bootability Specification 1.0 dated October 25, 2004; and UASP Bootability v1.0 dated March 4, 2013. These are library listing dates and revisions, not a claim that each is the newest applicable specification.
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- High-speed USB 3.0 performance of up to 150MB/s(1) [(1) Write to drive up to 15x faster than standard USB 2.0 drives (4MB/s); varies by drive capacity. Up to 150MB/s read speed. USB 3.0 port required. Based on internal testing; performance may be lower depending on host device, usage conditions, and other factors; 1MB=1,000,000 bytes]
- Transfer a full-length movie in less than 30 seconds(2) [(2) Based on 1.2GB MPEG-4 video transfer with USB 3.0 host device. Results may vary based on host device, file attributes and other factors]
- Transfer to drive up to 15 times faster than standard USB 2.0 drives(1)
- Sleek, durable metal casing
- Easy-to-use password protection for your private files(3) [(3)Password protection uses 128-bit AES encryption and is supported by Windows 7, Windows 8, Windows 10, and Mac OS X v10.9 plus; Software download required for Mac, visit the SanDisk SecureAccess support page]
What does a host see?
As one implementation example, Linux kernel 5.10 documentation says its Mass Storage Gadget appears to the host as a disk or CD-ROM drive. Each logical unit can use a regular file or block device as backing storage. In that implementation, a CD-ROM logical unit implies read-only access. These details describe the Linux gadget, not a guarantee about every USB storage device. See the Linux 5.10 Mass Storage Gadget documentation.
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What USB MSC does not tell you
- Filesystem: the class name alone does not identify how data is formatted on the storage.
- Speed or capacity: it does not establish a product’s practical performance, transfer rate, or storage size.
- Universal compatibility: the class label alone does not prove that a device works with every host or operating system.
- Transport: USB MSC does not mean BOT specifically; related specifications include CBI and UASP-related material.
Those details depend on the device, host, implementation, and applicable specifications. The cited documents do not provide a current cross-platform compatibility matrix or a comparative performance ranking.
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- What You Get - 2 pack 64GB genuine USB 2.0 flash drives, 12-month warranty and lifetime friendly customer service
- Great for All Ages and Purposes – the thumb drives are suitable for storing digital data for school, business or daily usage. Apply to data storage of music, photos, movies and other files
- Easy to Use - Plug and play USB memory stick, no need to install any software. Support Windows 7 / 8 / 10 / Vista / XP / Unix / 2000 / ME / NT Linux and Mac OS, compatible with USB 2.0 and 1.1 ports
- Convenient Design - 360°metal swivel cap with matt surface and ring designed zip drive can protect USB connector, avoid to leave your fingerprint and easily attach to your key chain to avoid from losing and for easy carrying
- Brand Yourself - Brand the flash drive with your company's name and provide company's overview, policies, etc. to the newly joined employees or your customers
Safe removal matters
For USB-powered storage, unmount or safely eject the device before unplugging it when the host provides that option. Linux kernel 5.10’s gadget documentation warns that unplugging without unmounting can cause data loss. Treat this as an operational caution; exact behavior depends on the device and host.
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- 【Metal Swivel Cap Design】USB thumb drive is metal swivel cover provides extra protection for the usb thumbdrive connector, no usb drive cap to lose; keychain design makes it easier to carry without worrying lose it.
- 【Wide Compatibility】USB drive supports Windows 7/8/10/11 / Vista / XP / Unix / 2000 / ME / NT Linux and Mac OS, also Supports USB 2.0 and 1.1 ports. USB Stick support TV, desktop, notebook computer, car, audio and other device. The USB Memory Stick is your great data storage and transfer companion with traveling and working.
- 【Easy to use】usb memory stick is plug and play without any software installation. Just simply plug the Flashdrive into the port of your USB-compatible devices such as computer, laptop to start data storage or transmission.
- 【What You Get】16 GB USB Flash Drive Thumb Drive, The default format of the usb storage flash drive is FAT32.
Rank #4
- GOOD VALUE PACKAGE - 1 Pack 32GB Memory Stick USB 2.0 Flash Drives with great cost performance and high quality.
- BIG CAPACITY - The available capacity: 29.10GB-29.8GB, You can save the data of movies, music, photos, designs, programs, manuals, handouts in a high speed.Good performance in digital data storing, transferring and sharing with families, friends, workmates, clients and machines.
- EASY TO USE & PLUG AND WORK - Support windows 7 / 8 / 10 / Vista / XP / 2000 / ME / NT Linux and Mac OS, Compatible with USB2.0 and below.
- TWISTTURN DESIGN & EASY CARRY - The metal clip rotates 360° round the ABS plastic body which with rubber oil skin feeling finish. The capless design can avoid lossing of cap, and providing efficient protection to the USB port.
- WARRANTY & SUPPORT - SIMMAX logo is laser printed on the USB connector surface, our products are of good quality and we promise that any problem about the product within one year since you buy.
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