Removable v. Fixed USB drives
- USB Hard drives are always the Fixed type.
- Most USB Flash drives (but not all) are of the Removable type.
- Microsoft Windows-Certified (WindowsToGo certified) USB Flash drives will be of the Fixed type.
The SCSI Inquiry Command
The removable media device setting is a flag contained within the SCSI Inquiry Data response to the SCSI Inquiry command. Bit 7 of byte 1 (indexed from 0) is the Removable Media Bit (RMB). An RMB set to zero indicates that the device is not a removable media device. An RMB of one indicates that the device is a removable media device. Drivers obtain this information by using the StorageDeviceProperty request.
Windows/linux will assume that a RMB=1 device can be disconnected at any time by the user. Any disk writes made by the OS to the media will be made immediately - no delayed buffering will be used. For a RMB=0 device (e.g. USB HDD), the OS may choose to delay writes for say 30 seconds or so. This improves performance because instead of lots of small write operations, it is quicker to use just a few large write operations.
For more information about the SCSI Inquiry command, see https://www.t10.org
RMPrepUSB will inform you of the type of USB drive you have:
Why is the Fixed\Removable type important?
E2B WinHelper Flash drive
One way of avoiding this is to also connect an E2B 'WinHelper' USB Flash drive.
This must be a Removable-type of USB Flash drive which contains a few 'WinHelper' files (see here for more details). E2B will also write the XML files to this Removable 'WinHelper' flash drive when you boot from a Windows Install ISO - thus the XML file will be found by Windows Setup and the ISO file will be mounted as a virtual drive.
Tip: Use a USB hard disk enclosure such as the Inateck FE2007 which has 3 USB ports, and simply connect a small Removable WinHelper flash drive to one of the 3 ports. Then you will always have the WinHelper drive connected.
If you do not want to use a WinHelper flash drive with your 'fixed-disk' E2B drive, you will need to convert the Windows Install ISO to a .imgPTN file.
Note E2B uses this XML file trick when booting some WinPE and other Windows-based ISOs too. Which is why the 'list of tested Payloads' page may say that some ISOs can only be successfully booted from Removable USB drives (unless you convert them to .imgPTN files).
Recommended for Easy2Boot (fastest flash drive!)
SanDisk Extreme SDCZ880-128G-G46
Fastest USB 3!
See Blog post