"Ask Dr. Micro" provides answers to workstation and microcomputer questions of general interest. Readers can submit questions by sending electronic mail to drmicro@garnet.berkeley.edu or calling 642-8899. The Workstation Consulting staff will reply to questions as quickly as possible. Answers to common questions are available through the Workstation Support Services World-Wide Web server (http://wss-www.berkeley.edu/). Dr. Micro had help from Seth Novogrodsky in answering this question.
Dear Dr. Micro: I know it is important for me to back up the information and software stored on my computer, but I don't know how to go about doing it. Can you provide me with some suggestions? --Emily Diskinson
Dear Emily: Dr. Micro is very glad you asked this question. Backing up is essential for all computer users who value their work and time. Every hard disk drive ever manufactured will fail at some point, quite possibly at the worst time imaginable. In addition, virtually all computer users will accidentally delete one or more important files on occasion. It is also possible your computer or hard drive may be stolen or destroyed in a disaster.
There is no better insurance against data loss than for you to make sure that your files are backed up regularly; Dr. Micro cannot overemphasize this point. The time and effort needed to make backups are insignificant compared to what it could take to recover data from a bad disk or recreate the data if recovery is not possible.
To make a backup, you will need three things: a backup device, backup software, and a backup strategy. The backup device can be a floppy disk drive, a tape drive, a high-capacity removable disk drive, another hard disk drive, or a backup system available through a network. The software can be a backup program that came with your computer or backup device, or a program you have purchased.
The backup strategy is the method that you will use to make sure your files are backed up regularly. For example, you can plan to do a complete backup of all your data once a month and incremental backups each time you use your computer; an incremental backup can save just those files that have changed or been created since your last full backup.
Below are a few points to consider when deciding how to back up your data:
The remainder of this article provides information on specific backup methods and resources that you can use to come up with a backup strategy that will work for you.
Hard disk drives now typically store from about 500 MB to more than 2 GB (a gigabyte or GB is equivalent to about 1000 MB or megabytes); a high-density 3.5-inch floppy disk stores about 1.4 MB. For this reason, backing up to floppy disks is often impractical. Nevertheless, using floppy disks to back up has the advantage that you do not need to buy any special hardware.
As mentioned above, it is important to back up the original diskettes containing the software you install on your computer, even if you use a different type of media for your regular backups. If you have a PC, you can use the DISKCOPY command in DOS or the "Copy Disk..." command under the File menu in File Manager in Windows 3.1, or Windows Explorer or "My Computer" in Windows 95 or Windows NT Workstation 4.0. If you have a Macintosh, you can use the free Disk Copy program; although you can use the Finder to copy diskettes, Disk Copy has the advantage of making exact copies. (Disk Copy is available at http://cobweb.berkeley.edu/Web/Unsupported/Disk_Copy/Docs/Summary.nclk and on the "Supported Software" volume of the Cornucopia file server in the folder "Pgms to copy disks & read files." Cornucopia is available through AppleShare in the "Workstation Support" zone, FTP and Gopher [cornucopia.berkeley.edu], and the World-Wide Web [http://cobweb.berkeley.edu/Cornucopia.nclk].) It is especially important to make copies of your operating system diskettes and the applications you use most often. After making the copies, you should put the original diskettes in a safe place, preferably in a different room or even a different building.
If you decide to make floppy disks your primary backup medium, there are steps you can take to make backing up simpler:
Although backing up on floppy disks is not practical for backing up high-capacity hard disks in their entirety, it can be useful in some situations.
Backup devices fall into two rough categories: tape and disk. Which type of device to choose depends on your particular needs. In general, tape has the advantage of lower cost for media and larger capacity, making tapes a good choice for backing up entire disks. If you choose a tape backup system that has a capacity greater than that of your hard disk (or hard disks, if you have more than one), then you will be able to have the backup done unattended or in the background without having to worry about changing the tape. Tape drives are sequential-access devices, which means that all data on the tape must be read and written in sequence; that is, to get to information earlier on the tape, the drive must rewind the tape (just as with audio or video tape).
Backup devices that use disks have the advantage of random access, which is the ability to access data readily out of sequence. The random access capabilities of disk-based backup devices make them practical for storing data that you do not want to store, or do not have the capacity for, on your hard drive (although you would still need to back up those disks as well). These devices are often faster at transferring data than tape drives. The capacity of the removable disks is often smaller than that of many hard drives, requiring multiple disks for a complete backup. Speed typically ranges from that of a very fast floppy disk drive to hard disk speeds. In addition, you can readily use disks to exchange files that are too large to be stored on floppy disks with other computer users who have the same type of removable disk drive. Finally, in the event of a hard disk failure, you may be able to boot up from your backup disks, a capability not normally provided by tape.
Regardless of whether you choose to use disk or tape, the key factors for choosing the right device are the same: speed, capacity, and cost and durability of media.
Tape drives. Different types of magnetic tape drives are available, varying in cost, speed, and the type of media used. The capacity of any given tape drive is determined by a number of different factors, including the length of tape used, compression techniques employed by the backup software, and compression technologies that may be incorporated into the hardware components of the tape drive itself. Hardware compression can increase the capacity of a tape by as much as several times. Depending on the data you need to back up, software compression can often double the capacity of a tape. In many cases, hardware and software compression should not be used together, since performance may suffer with little or no benefit. The capacities of the types of tape listed below generally assume no software compression is used, except as noted. In any case, it is most often best to purchase a tape drive that can accommodate a full backup on a single tape.
The tape drives most commonly used with personal computers include the following:
Other tape formats include 8-mm helical scan tapes and DLT tapes, which are often used for workgroup backups.
Removable disks. As with tape devices, you have a variety of choices available to you when selecting a disk-based backup system. All capacity figures below refer to uncompressed data. The most popular types of these devices include the following:
One of the most popular types of cartridge drives is the Zip drive, developed by Iomega. Zip drives use both hard drive and floppy drive technology and can store 100 MB per disk. The Zip disks cost about $15 to $20 depending on quantity, and the drives themselves are available for as little as $150. Some new computers are now shipping with Zip drives as standard or optional features. Although the contents of an entire hard disk typically cannot fit on a single Zip disk, a Zip drive may be fine for backing up important data files. (Both Zip drives and Jaz drives are available from the campus computer store, The Scholar's Workstation [http://www.tsw.berkeley.edu].)
Unlike Iomega and SyQuest drives, the magneto-optical disk drives are not built around proprietary standards and are available from several manufacturers. MO disks have the advantage of being virtually immune to magnetic fields and can be a good choice for archival storage. (Recordable CD-ROM drives use a similar technology, although they do not allow data to be erased. They are also very good for archival storage and are coming down in price. Another relatively new option in optical disk drives are PD/CD-ROM drives, which can read and write to special 650 MB optical disks and also play standard CD-ROMs.)
Which of these types of disk drives would be best for you depends in large part on how many disks you will need and the performance you require; the cost of the disks can be significant, often greater than the initial investment in the disk drive itself.
It is important to keep in mind that these technologies are constantly changing. For example, recently a number of vendors have developed a new type of diskette drive that can read and write to existing 3.5-inch diskettes and also use new a 120 MB capacity diskette (LS-120 diskettes), which may provide stiff competition for Iomega's popular Zip drives.
If your computer is on a network, backing up over the network may be the best solution. With a network backup, only the administrator of the network needs to be concerned with changing the media, making sure that the backup device is ready, and so forth. Before choosing another backup solution, check with your system administrator or computer support person to see if a network backup solution is available.
Network backup solutions fall into two rough categories: server-initiated and client-initiated. With a server-initiated approach, the server automatically initiates the backup at a specified time. An example of a product that uses this approach is Retrospect Remote, which a number of departments on campus are using to back up workgroups of Macintoshes. (The Letters & Science Computer Resources group [http://www.ls.berkeley.edu/lscr/] is currently evaluating the Retrospect Remote client for Windows as a possible solution for backing up the PCs of its users.) For more information on Retrospect Remote and workgroup backups, please see To move forward, you must back up in the July-August 1993 Berkeley Computing. Typically, the backups are scheduled to occur at night, and the Macintoshes may be shut down automatically after the backup is complete.
With a client-initiated approach, the software on the individual computer sends a message to the server, indicating that it is ready to be backed up. Some products, such as IBM's cross-platform backup product ADSM, can use either approach. (Central Computing Services [CCS] is providing a service for the campus for backing up Macintoshes, PCs, and UNIX workstations on the campus network using ADSM with a central computer as the backup server. For information on this service, please see IST announces UCBackup, the over-the-Internet backup system in the September-October 1995 Berkeley Computing and Communications or the UCBackup home page at http://garnet.berkeley.edu/~uc backup/.)
If you do not need to have your entire hard disk backed up, one solution in a networked environment would be to keep your important files on a file server that is backed up regularly.
Choosing the right backup software can be as important as choosing the right backup hardware and media. You may already have backup software; some computers, operating systems, and backup devices come with backup programs, as do a number of general utility packages such as the Norton Utilities for Macintosh. (Dr. Micro recommends that all personal computer users have at least one general disk utility package in any case.)
Features that you may wish to look for when evaluating backup software include the following:
Reviews in computer magazines can be a good source of information on backup software, particularly in regard to performance and ease of use; see below.
Because backing up is such an important activity for computer users, it might a good idea for you to do some research before choosing the best approach for you. Two resources that were useful in preparing this revision of this article were the Usenet newsgroups comp.sys.ibm.pc.hardware.storage and comp.sys.mac.hardware.storage. Articles in computer magazines are also an excellent source of information about backup hardware and software; for information on accessing computer magazine articles through the Internet, please see Ask Dr. Micro: How can I find answers to computer questions through the Internet? in the November-December 1996 Berkeley Computing and Communications. In addition, the original version of this article (Ask Dr. Micro: How can I back up the files on my computer? in the April-May 1995 Berkeley Computing and Communications) includes a listing of a number of useful articles about backups.
Berkeley Computing & Communications,
Volume 7, Number 2 (April-May 1997)
Copyright 1997, The Regents of the University of California