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Backups and Drive ImagesEric Moore, CUGGJune 14, 2003 |
Introduction
For those of you who did not attend the CUGG meeting on November 9, 2002, Lowell Shatraw gave a good presentation on disk imaging software, such as Symantec Norton Ghost™ and PowerQuest Drive Image™. He shared much information about the various products available on the market and their advantages. However, I sensed that not everyone may have fully understood what these products are for. In order to supplement the information he gave in his presentation, I decided to write a short article about disk imaging software—its advantages and disadvantages—and how I use it in my regular backup strategy.
Traditional
Backups and Disk Imaging
The chief similarity that traditional backup software (e.g. Microsoft Backup) has in common with disk imaging software is their ability to back up files and folders on your computer to various media types, such as a second hard drive, Zip™ disks, CD-R, and CD-RW. One of the most important things you can back up is your Windows operating system, which allows you to recover painlessly (more or less) from serious problems such as a failed hard drive or a computer virus or worm. One of the disadvantages of Windows-based back up software in general is that you may not be able to restore data without first starting Windows. This is would be a problem in the event that you cannot start Microsoft Windows. Unless the software provides an emergency recovery utility (usually in the form of a program that runs from a bootable floppy disk) that enables you can restore Windows from MS-DOS mode, you will have your work cut out. You will first need to reinstall Windows or restore using a recovery CD provided by your PC manufacturer before you can use the backup software to restore the lost information. (I do not have experience with the recovery CD’s that are provided by PC manufacturers, but I do know that installing Windows 98 from scratch with a standard installation CD takes approximately 40 minutes on a vintage 200 MHz Pentium-based system.) After installing Windows, you will also need to reinstall the backup software before you can finally restore your programs and/or data. Depending on the amount of data to restore and the speed of your computer, this could take at least half an hour. Even so, using a traditional back up application is a good idea—certainly better than not backing up your critical information at all.
The main advantage of disk imaging software is that it will allow you to back up and restore your entire Windows operating system, even if you cannot start up Windows (even if you run Windows Me or 2000, which do not have an MS-DOS mode). This is done using a DOS-based application which is run from a bootable diskette. In order to understand the mechanics of how a disk image is performed, a basic understanding of hard drives and partitions is in order.
Hard Drives and Partitions
The hard drive is the piece of hardware that serves as the storage device for your files and programs. It consists of one or more disks, like those in a diskette, except that they are made of a rigid material such as metal, glass, or ceramic. Each disk is coated with a magnetic material in which your programs and data are encoded. Unlike RAM (random access memory), the information on a hard drive persists even if your PC is turned off. This is the reason why when you are working on a document, you need to be sure to save it periodically to your hard drive (or some removable media such as a CD-RW). As long as the file is not deleted or overwritten, and the hard drive is not exposed to a strong magnetic field, it is safe. Information in RAM persists only as long as the PC has power. This is why if you are working on a document that you have not saved and the power in your home goes out, the RAM “forgets” everything and your unsaved information is lost.
Before programs and data may be saved to a hard drive, it must first be partitioned. If you every buy a PC system from a company such as Dell or Gateway, this will have already been done. If on the other hand you ever decide to buy and install a new hard drive, you will need to partition and format it before using it. Without going into too many technical details, partitioning is essentially a means of subdividing the space on a hard drive into one or more drive letters. For instance, if you have a single hard drive with only one partition, then the only hard drive letter you will have access to is C. If it is divided into two partitions, you will have two hard drive letters: C and D. (These examples omit the fact that you may have other drive letters for a second hard drive, the floppy drive, a CD-ROM drive, etc.) For instance, my PC has two hard drives which are divided into five partitions—A through G.
The question you might ask at this juncture is: Why divide a hard drive into multiple partitions? One of the reasons for hard drive partitions is that the PC and/or Windows may require it in order for you to use the maximal amount of space on the drive. For instance: MS-DOS, Windows 3.1, and the original edition of Windows 95 could only “see” partitions no larger than two gigabytes. When new multi-gigabyte drives became commonplace, this created a problem. If you decided to buy a new 4-gigabyte drive, you could only use two gigabytes of the space…unless you divided the drive into two or more partitions of two gigabytes or less. Likewise, if you bought a 6-gigabyte drive, you would need to divide it into at least three partitions of two gigabytes or less. (If 100 GB drives had been available back then, you would have needed to divide it into at least 50 partitions!)
Another reason for partitioning is to create a logical division of hard drive space for the various types of programs and files you keep. For instance, I have a 2 GB partition for Microsoft Windows and some applications, another 2 GB partition for third-party applications, a 10 GB partition for my file archives (old data files and downloaded software), and a 4 GB partition for my backups.
Backups Using Disk Imaging
Whereas the chief similarity of traditional backup software and disk imaging software is their ability to back up files and folders to various media types, the chief difference is how they back up the information. A traditional back up program such as Microsoft Backup allows you to select which folders and files you wish to back up. You may select individual files, entire folders, or the entire contents of a hard drive. A disk imaging program only allows you to back up individual partitions, or all of the partitions on a hard drive. It is for this reason that a drive imaging program is not appropriate for everyone. First, this is more time-consuming than if you only need to back up some of the files and folders on a partition. Second, depending on the size of the partition or hard drive, this can create enormous files, sometimes with a size on the order of a gigabyte or more! Having a second hard drive with ample space provides a relatively quick solution to saving the image file, while saving the image to removable media such as CD-R could is slower and may require several disks. On the other hand (as stated before), a disk imaging program allows you to restore the information without first reinstalling Windows.
When restoring data from a disk image, you need to be careful that you understand what you are doing. Whereas performing a full restore with a traditional backup program can overwrite your files, performing a full restore from a disk image WILL overwrite every file and folder on the partition. If you restore to the wrong partition, you will lose everything in that partition.
My Backup Strategy
For example, at the beginning of every month, I use PowerQuest Drive Image™ to create an image file of my C: drive, which is devoted primarily to Microsoft Windows 98. Since most of my applications are installed on E:, I can save the entire contents of C: to a compressed image file with a size on the order of 620 megabytes, just small enough to fit on a single CD-RW. Just to be safe, I have a redundant backup system: in addition to CD-RW, I also save one copy of the image file to a partition (F:) on my first hard drive and a second copy to another partition (G:) on my second hard drive. If either of my hard drives should fail, or for some reason I cannot read the contents of the CD-RW, I will still be able to restore from one of the other two copies of the image file.
In the event that I should ever be unable to start up Windows, I can easily restore Windows back to the working state it was in when I last imaged the drive. I estimate the entire time to restore would be about twenty minutes, less time than it would take for me just to reinstall Windows on my 300 MHz Celeron-based PC. Because of space limitations and the time it takes to create an image, I only perform a disk image once a month. For my daily and weekly backups I use Microsoft Backup to back up only those files and folders that have changed or been created since the last backup. Therefore, after restoring from the disk image, I would also need to restore from the daily and weekly backups in chronological order to complete the restoration process.
Other Benefits of Disk Imaging
Before closing, I will briefly mention two other benefits of a disk imaging program. First, if you ever decide to buy a new hard drive and transfer everything including Windows from the old drive to the new drive, you can do this with a disk imaging program. Second, if you do not already have a Windows recovery disk, you can create a recovery disk of your own. After installing Windows and any other software you need, you can then save your work to an image on a CD. Then you have a failsafe means of restoring your system at a later date.
Conclusion
In conclusion, you can use drive imaging software to save yourself time and trouble when saving, restoring, and copying information on a hard drive. However, it is probably not a necessity for most people. If your back up needs are modest and performing a “quick” system recovery is not important to you, then I would not recommend the investment. In addition to the cost of the software, you must be sure you have a good understanding of hard drives and partitions. Otherwise, you may lose your data—especially if you make a mistake and restore an image to the wrong hard drive or partition.