"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, by calling 642-8899, or by visiting the consulting office in 264 Evans Hall. The Workstation Consulting staff will reply to questions as quickly as possible. Answers to common questions are available through the Workstation Support Services Gopher (wss-gopher.berkeley.edu, port 70). 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 something that all computer users who value their work and time must do routinely. Every hard disk drive ever manufactured will fail at some point, and Murphy's Law and at least one large supplier of hard disks predict that it will happen at the worst possible time. In addition, virtually all computer users will accidentally delete one or more important files at some point. 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; it is not possible for Dr. Micro to overemphasize this point. The time and effort needed to make backups are insignificant compared to the time and effort 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 a commercial program that 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 on doing 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 80 MB to more than 500 MB; a high-density 3.5-inch floppy disk typically stores about 1.4 MB. For this reason, backing up to floppy disks may be 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 disks of 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 "Disk Copy..." feature of the File Manager in Windows. 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 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://cornucopia.berkeley.edu/].) 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 always an ideal solution for everyone, it can be practical for many users and can save you a considerable amount of grief.
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. If you choose a tape backup system that has a capacity greater than 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 sequentially; that is, to get to information earlier on the tape, the drive must rewind the tape (just as with an audio tape recorder or VCR).
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 generally smaller than that of many hard drives, requiring multiple disks for a backup. Speed typically ranges from that of a very fast floppy disk drive to hard disk speeds. In addition, you can use disks can be used to exchange files that are too large to be stored on floppy disks with other computer users. 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 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 several times. Depending on the type of 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. The capacities of the types of tape listed below generally assume no software compression is used. In any case, you should 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:
The high capacity QIC drives, DAT drives, and 8-mm helical scan drives can be good choices for backing up a workgroup. (See "Backing Up over a Network" below.)
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:
SyQuest cartridges are similar to ordinary hard disks except that the cartridges contain just the magnetic platters on which information is stored, not the drive mechanism itself. SyQuest cartridges come in 5.25-inch and 3.5-sizes and have capacities ranging from 44 MB to 270 MB. Prices for SyQuest cartridges range from about $42 to $75, and prices for SyQuest drives generally start at around $400. SyQuest drives offer performance comparable to many hard drives.
Bernoulli drives use both hard drive and floppy drive technology. The capacity of Bernoulli cartridges ranges from 44 MB to 230 MB. A 230 MB cartridge costs about $90, and prices for Bernoulli drives start at about $400. Speed is close to that of a SyQuest drive. In addition, Iomega has recently announced a new type of removable drive that uses a new type of disk cartridge called a Zip disk, using technology similar to the technology used in Bernoulli drives. According to Iomega, a Zip disk with a capacity of 100 MB will cost about $20 and the drive itself will cost about $200 for both Macintoshes and PCs.
Unlike Bernoulli 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, which use a similar technology, are also very good for archival storage and are coming down in price.)
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.
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 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. (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 currently testing a pilot 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. When the ADSM service is in production, CCS will be working with campus departments to coordinate its use.)
For more information on network backups, please see the articles referred to below under "For More Information."
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 PC Tools, MacTools, and 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. The articles listed below were helpful to Dr. Micro in preparing this article and may be helpful to you as well:
Articles for which the full text or abstracts are available through the Computer Articles Database on MELVYL are marked with an asterisk (*) in the list above; for information on accessing these articles, see the Berkeley Computing articles "New MELVYL Databases Online" (January-February 1992) and "Find It, Save It, Mail It!" (July-August 1993). If you have further questions on this topic, please feel free to contact Dr. Micro.
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