Windows Vista's Image-Based Installation
This article was published by ComputorEdge, issue #2502, , as a feature article, in both their print edition (on pages 19-20) and their website.
Every modern computer operating system comprises hundreds of files, organized into dozens of directories, consuming many gigabytes of hard disk space. As a consequence, the installation of such an operating system (OS) on a hard disk drive, can be quite time consuming, as the installer program creates the directories and their subdirectories, unpacks all of the needed files, and writes them to the hard drive.
For a computer user who purchases a new system with the OS preinstalled, or purchases a new system with a blank hard drive and thus only has to install the OS once, the installation time is not a major problem. But for computer hobbyists who typically install separate instances of an OS on multiple partitions on their hard drive, and even on multiple hard drives, the installation time can quickly- er, slowly, turn into an unpleasant ordeal.
Microsoft's flagship OS, Windows, is no exception. The latest version of Windows, Vista, comprises even more files than any of the earlier versions, and requires a minimum of 20 GB of hard drive space for the installation, and another 15 GB of free space just to run. To earn the title of "Vista Premium", a PC needs a minimum of 40 GB for the install and another 15 GB free space, for a total of 55 GB just for the OS.
The bottom line is, installing Windows Vista from one or more CD-ROMs — at least, if done the traditional way — would take even longer than the time needed to install Windows 2000 or XP.
Digital Video to the Rescue
But as operating system and computer application vendors continue to increase the capabilities of their products, thus forcing the hardware vendors — and the hapless computer consumer! — to keep increasing the capabilities of their PCs and Macs, there is usually at least one component in those personal computers that can ease the process of installing operating systems and applications: a DVD drive. With a data storage capacity more than 10 times that of a CD, a DVD is making possible some new options for digital product delivery and installation.
As more PCs come with a DVD player preinstalled, and more people add DVD players to older systems that lacked them originally, Microsoft is taking advantage of this by releasing Windows Vista on DVDs, instead of on CD-ROMs exclusively, as they did with Windows 2000 and XP. The greater capacity of a DVD disk has allowed Microsoft to take a radically different approach, in which the DVD contains not an installer and the archive files that it works on, but instead an entire preinstalled copy of Vista, in an image, that then gets decompressed onto the PC's hard drive.
In particular, the DVD contains a Windows Imaging (WIM) file, which is essentially the entire Windows Vista OS, wrapped up into one image file. If the user is doing a clean install of Vista, then the .WIM file is unwrapped and copied directly into the target partition on the hard drive. If the user is doing an upgrade to Vista, then their settings in their older version of Windows can be saved temporarily, Vista is uncompressed onto the hard drive, and the user settings are applied to the freshly installed Vista.
Some users, especially those burned by problematic OS upgrades in the past, may not trust the Windows Vista upgrade process to work correctly. Instead, they may want to do a clean install of Vista, and only then apply their personal settings from their previous version of Windows, such as Windows XP. The Windows Vista installation process makes this possible, when the User State Migration Toolkit is utilized to save those settings prior to the older version of Windows being wiped out by the clean install of Vista.
Note that the User State Migration Toolkit can only retain user settings from Windows 2000 and XP, and it is a command line tool, and thus not as user-friendly as Microsoft's Files and Settings Transfer Wizard, which has a more newbie-friendly graphical user interface (GUI).
In addition to speeding up the Windows installation process, the new image-based approach introduced with Windows Vista offers some additional benefits. Users apparently do not have to be concerned about their personal data in the target partition being wiped out, because the image is file-based, and not sector-based, and thus no user files are deleted or overwritten during the process.
The fact that the Vista image is file-based also means that the WIM file format is completely independent of any hardware. This alone would confer no advantage when installing from the Vista installation DVD onto the hard drive. But when going in the other direction — backing up a copy of Vista, including one's personal settings, into a WIM file — then the user could later install that on a completely different PC or laptop, from a different vendor. Prior to use of the WIM file format, this was not an option for backing up and restoring Windows using the native installation process only.
This may have an impact upon the software vendors who make and sell products that allow you to make image copies of partitions, including one containing Windows, for later restoration to a new hard drive (such as when your existing hard drive dies) or back to the original hard drive (such as if and when you decide to repartition the hard drive, for whatever reason, and you do not trust any repartitioning tools). Since one of the most common uses of those third-party imaging applications is for the backup and restoration of OS partitions, the WIM file format could make their products unnecessary for most such users.
But as the Redmond giant giveth, it can also taketh. For instance, device driver installation files are increasingly being provided in the form of executables (.exe), which put the needed device files in the correct locations within Windows — as opposed to being a single .sys file that the Windows device manager installs completely. The device driver executables are run during Windows Vista installation in part seven of the process, after Vista has been built, and before user login. This process of course takes place before the user has had a chance to install anti-malware protection. Consequently, some advanced users worry that malware-infected driver executables could inject themselves into the WIM installation file.
Also, for those advanced users interested in slipstreaming Windows Vista with all of the patches from Windows Update, each patch would have to be downloaded and applied individually, using a command line.
Yet overall, Windows Vista's new image-based installation and customization capabilities would seem to offer more advantages than disadvantages, and could easily become the new standard for the packaging of Windows.