Guidelines for Disk-Cloning

What to Look for in a Cloning Solution

  • Imaging assistance: Should you do the imaging yourself or pay a third party? Computer manufacturers, resellers and other companies are happy to clone your computers for a price. The larger your order, the more likely you can benefit from this type of arrangement. Cloning 100 or 200 computers in your library can put a serious strain on your network and your IT department staffers.
  • Maximum limits: What’s the maximum number of computers that the software can handle simultaneously?
  • Efficiencies: How does the cloning software react to differences in hardware components? If you have two batches of PCs with similar components, you may be able to clone both with a single image. This can save you time and disk space. Also, can you restore individual files from your disk image without restoring the entire disk? In other words, can you browse the image as though it were a file system and pull out a single file or a handful of files? With the current versions of most cloning programs, you can do this.
  • Software capabilities: Will the software perform incremental updates? In this sense, cloning software is becoming more and more like backup software. It scans your source computer for recent changes and incorporates them into the master image without forcing you to shut down or reboot. Also, creating a full image can really hog your library’s network and computing resources. These small, incremental updates are much more efficient.

What to Consider When Implementing a Cloning Solution

  • Hardware purchases planning: For cloning to work effectively, you need to have a minimum number of different hardware models. If you buy a few computers here and there, you’ll wind up with a patchwork environment, and you’ll have to manage dozens of different disk images. More is not better in this case. For more on this topic, check out our coverage of Standardizing Your IT Infrastructure.
  • Master disk images planning: Who creates the images? Who decides what software to include and how to configure that software? Remember, these disk images may be deployed to dozens of staff computers or public computers, so the affected parties should have a voice in the development of the image.
  • Source image preparation: Microsoft Windows operating systems come with a utility called Sysprep that strips out all unique, specific information (e.g., computer name and security identifier) from your source hard drive and gets it ready for cloning. Nlite is an open­-source program that lets you strip out Windows Media Player, Outlook Express and other add­-on features from Windows XP (but not Vista). These preparation utilities are often used in concert with post­-cloning tools such as, Setup Manager and Ghostwalker. (See "Tweaking and customizating" for more details on these tools).
  • Image deployment: You can always perform a direct disk-­to­-disk copy of an image. In other words, your source and destination hard drives are connected to the same computer, or they’re connected via a network. The transfer is direct, without any intermediate steps. However, many librarians and systems administrators create a “master image” and then deploy from that. The master image is usually stored on a removable hard drive or a network drive (see "Testing"). When you have a large number of computers to image, you should consider deploying the image across the network. Using a technology known as multicasting, most disk­-cloning programs can image dozens of computers at the same time. Multicasting may slow your network down somewhat (do it after hours or during non-­peak hours), but it was designed specifically to send lots of information to lots of computers with the least possible overhead and bandwidth use. It won’t choke your network as long as your network infrastructure is relatively up­-to-­date. Also, if you’ll be cloning and multicasting on a regular basis, you should consider dedicating a server to the process.
  • Testing: If you’re cloning lots of computers, image one or two and examine them carefully before deploying to your entire library. Check that your image is reliable and uncorrupted. Also, look again to make sure that you haven’t forgotten an important setting or an important piece of software.
  • Tweaking and customizing: Your computers might be 99 percent identical, but that last 1 percent is still important. After you’ve cloned your PCs, you need to change the name of each one to avoid conflicts on the network. If your computers use static IP addresses (increasingly rare), you should assign these manually to each machine after they’re imaged. In a Windows domain environment, you also need to assign a special identifier (called a SID) to each machine. Often, your cloning software will have a tool that can handle this automatically (e.g., Ghostwalker or Setup Manager).
  • Image storage and management: With most cloning software, you can save your images to a local hard drive, a network drive, a tape backup, CDs or DVDs. Avoid CDs and DVDs if you can. Since most images won’t fit on a single CD or DVD, you’ll have to span your image across multiple disks. However, once you’ve saved your master drive to a local hard drive or a network drive, you can use DVDs to create backups of these images.

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