Ultra-detailed USB disk system knowledge sharing

1, EWF, FBWF defects, and the first time card machine problem.

As a result of the ordinary U disk write speed but only a 5mb/s, and ordinary hard drive is often more than 50mb/s, so, XP in the ordinary U disk Run "giant card", Microsoft in xpembedded provided EWF and FBWF can be written to the disk redirect to memory, just so that the general U-you XP has practical value.

But why EWF is more suitable than FBWF. There are 3 main reasons: First, because the U disk with the use of NTFS compression can save 1/3~1/2 disk space, at the same time because of the reduction of absolute disk read and write, thereby easing the U-read speed bottleneck, so the use of NTFS compression is a U disk XP best choice, EWF support NTFS compression, But FBWF doesn't support it. Second, EWF has a write filter in effect, do not need to restart the switching state, you can immediately save all, and FBWF does not have this function; Although you can invoke the API enumeration file provided by Microsoft for real-time synchronization, you cannot save the folder and save the stability and speed of the EWF. Third, because EWF is the bottom of the whole disk filtration, FBWF is the top of the file filter, software compatibility is worse than EWF.

But "Chengye, Xiao", EWF also brought serious problems, the most important, because the writing system disk is written memory, the system used in temporary files is unavoidable, especially the internet to see movies, installation software, such as a large number of write system disk, resulting in large system memory consumption, the system more and more slow, lost response, the last downtime.

The EWF is invalid when the system image is first installed on a new USB drive. This is the search device, such as a large number of small files to disk, often resulting in the system "big card", and, because the EWF is invalid, forced to save system settings, if you want to keep the system good mobility, is the system pure good, forced to save on mobility is obviously unfavorable.

The WES2009 document clearly states that EWF cannot completely block all writes for an NTFS partition. If you use a USB hardware switch, start the blue screen. There is a "robot dog test" that unlocks the file after administrator privileges are enforced, and files such as C:windowssystem32conime.exe will be permanently changed in an XP system where only EWF filters are in effect. There is a strike program that calls CreateFile to write directly to the first sector of the disk, which is valid under both XP and Windows7, because EWF and FBWF do not protect the first sector of the disk, which results in all loss of disk data. Sometimes in EWF and FBWF protected Systems, the user's own disk partition changes, such as changing the active partition, will cause the system not to start, and EWF and FBWF can do nothing about it. Because FBWF and EWF can not intercept all write operations, resulting in shortened U disk life, System accidental damage.

　　2, USBXP device installation can not automatically "next" problem.

There is also a problem, the XP system in the installation of device-driven, not like Win7, will automatically "next", often the mouse hand cramps, and sometimes, for example, the use of the classic depth of 6.2 streamlined system made of usbboot, in only the USB mouse and keyboard machine will not install.

　　3, installation problems.

Microsoft's XPE (WES2009) installation is manual labor, Usboot has been relatively easy, the current network published more popular. The mirrored file for the Gho.

WES7 to install to USB is much simpler than xpe, download this oldtreeusb.xml and Microsoft IBW, follow the prompts to install USBWin7 to the USB disk. Install USBWin7, is the above registry file directly import, and then this system mirroring using ImageX or ghost Copy to the USB disk, set MBR boot.

This is not a problem for professionals or people who like to toss the system. But for the purpose of just trying to use a convenient, or a professional, this installation is too complicated, but also prone to human error.

　　4, USB device limit virtual memory problem.

Microsoft's USB patch and Usboot do not support the virtual memory set on the USB disk, which causes the system to run a large number of tasks, the system even installed on the USB hard disk and SSD also has obvious limitations. If the system memory fixed to the hard disk, when there is no hard drive, the system error, in addition to the system instability, but also the system to lose mobility.

　　5, the mobile system does not start from this system to be damaged problem, not all USB disk read write protection switch.

　　6, the system disk capacity small compatibility problem.

U disk capacity is limited, as a system disk, often software installation, use, such as newspaper disk space is not enough problems, resulting in poor system compatibility, this is a U disk system of a stubborn disease.