In-Depth

Smaller Is Better

ImageX is a slick compression tool that can help with Windows Vista deployment, as well as everyday file compression.

• By J. Peter Bruzzese and Tim Duggan
• 06/01/2007

ImageX is Microsoft's new command-line tool for creating, modifying and deploying .WIM image files (.WIM is the Microsoft Windows Imaging Format). Looking at Vista's installation image -- install.wim -- gives us a view of ImageX's compression abilities. The install file is about 2GB to start, which expands to about 8GB when you install Vista. That got us thinking -- what else could ImageX crunch down with that amount of force?

ImageX vs. the Other Guys
We ran a few benchmark tests of ImageX against some popular zip tools (WinZip, WinRAR and Windows built-in compressed folders) to see what it could really do. ImageX is a command-line utility. In all fairness, we're not huge fans of the command line. In this case, though, we readily admit it speeds up the process and conveniently lets you script practically all ImageX abilities. Plus you'll be using the same two or three commands every time.

We'll go through the examples step by step. For the first test, we compressed 1GB of music files using a folder called "Music" on our D: drive, which was stuffed with a random collection of MP3s. Here are the results after selecting "Maximum Compression" using our popular tools:

WinZip - 1 GB
WinRAR - 1 GB
Windows Compression - 1 GB

Then it was ImageX's turn. We have the ImageX utility on our C: drive, for simplicity's sake. Otherwise, we'd have to navigate to the directory where it's located. Here's what we entered: imagex /capture /compress max D:\Music D:\music.wim "musicimg".

ImageX has a variety of switches from which to choose. The ones we're focusing on here are "/capture," which tells ImageX that we want to create a .WIM file, and "/compress," which lets us set the compression level by following it up with Max | Fast | None after a space.

The result was 1GB -- not so hot. For this first example, though, we used MP3s, which are already pretty well compressed. There isn't much room for improvement. The same would be true of video files. You won't get an .AVI to compress much further.

Up next was a handful of Word, Excel and PDF files, totaling 1GB in a folder called "docs." The results were:

WinZip - 620 MB
WinRAR - 656 MB
Windows Compression - 689 MB

ImageX came in at 680MB. It only beat the built-in compressed folders. Finally, we tested with a folder filled with 1GB worth of multiple copies of the same document. WinZip, WinRAR and Windows compressed folders all kept the folder at 1GB with maximum compression. ImageX created a .WIM file that weighed in at 1MB. It took the multiples copies and shrunk them down to one. That validated our initial thoughts of ImageX's capabilities.

The reason for this is ImageX's ability to perform single instancing. Essentially, if you're compressing a folder that has more than one instance of a file, instead of compressing that file twice, it images one copy and points to other copies from that single copy image. A file getting copied over and over again happens all the time, especially on a file server.

You may never use ImageX to replace a simple compression tool, but you can create .WIM files and use its compression capabilities to create an image of folders, an entire disk or even your entire OS.

ImageX vs. CompletePC
In a rapid deployment scenario you'd install Vista plus any patches or applications. Then you'd seal the image with sysprep before booting with your Windows PE CD and using ImageX to create your deployment image. However, you could also use ImageX to make an image of your personal system. Not only is imaging your system a great way to create backups, you can also create multiple images for demonstration purposes.

We decided to test ImageX against Vista's CompletePC backup for disk imaging purposes. We started with a system running Vista Ultimate, using 77.6GB of disk space. We performed a CompletePC backup. The end result was a .VHD file (which is fully mountable, so you can retrieve any of your backed up files at a later time) weighing in at 32.4GB. It took a total of 41 minutes and 53 seconds to complete. This was an interesting result, because most of what we'd heard about CompletePC backups was that there's no compression and it's a one-to-one ratio.

Next, we needed to test ImageX. We created our Windows PE disk, booted the system from the disk (which took us to the command-prompt) and ran ImageX. It failed at first. We had to create an exclusion list called wimscript.ini and place it in the ImageX directory. This exclusion list would filter out the page file, hibernation file, the "System Volume Information" (the source of the errors) and any other file types we wanted to exclude.

The wimscript.ini file looks like this:

[ExclusionList]
Ntfs.log
Hiberfil.sys
Pagefile.sys
"System Volume Information"
RECYCLER
[CompressionExclusionList]
*.mp3
*.zip
*.cab

You can add or remove elements from the list. For testing purposes, we didn't want to exclude too much because this would conflict with the findings. This was one benefit of ImageX over CompletePC (which does a full system backup, no questions asked) -- you can choose not to back up specific files or file types. We were able to create the exclusion list from within our Windows PE environment using an old friend called Notepad.

We ran through the process without compression the first time and maximum compression the second time. We ended up with our non-compressed version shrinking down to an impressive 24GB. The compressed version came in only a little smaller at 23.5GB. It took the non-compressed version one hour and 28 minutes (much longer than CompletePC) and the compressed version took almost three hours.

These time frames or compression results aren't constant. Each system and each set of files is different, so each zip, backup or compression will yield varying results. The main point here is the flexibility of ImageX.

So what does all of this teach us? What is ImageX really good for? You can use ImageX to compress files and folders, but where it really shines is in imaging systems. In fact, in many ways it outshines the built-in CompletePC tools. While CompletePC has simplicity and speed, ImageX gets better compression and can filter out unwanted files in the backup.