Welcome to the October issue of MicroMetric's TipSheet. This monthly newsletter is targeted at addressing the needs of our customers. This month we'll expand the TipSheet (for the first time) to four pages, in order to present a complete set of tips on Backups in a single issue.
A backup is a second copy of selected files on your hard disk. It is a snapshot in time, in that the backup file copies may not contain the most recent changes made to these files, and they now may be different than those on currently on your hard drive. Backups normally serve two purposes - they allow retrieval of a file or files that have been damaged since the last backup, and they aid in the recreation of your system after a catastrophic failure, such as your hard disk drive's death. A backup can be as simple as copying your Quicken files to a floppy diskette after you write checks each month, to as complete as every file on your hard drive, including the current status of the Windows 95 registry. But unless you establish a routine, odds are that someday you'll really wish that you'd done a backup a day after it's too late.
Nobody likes to do backups. In general, they are an unproductive use of ones time. UNLESS. When something goes wrong, and you can retrieve lost data from your latest update, you feel like maybe it was worth it after all. Look on backups as a continuing insurance policy on your data - sooner or later, not if, something will go wrong with your hard disk. What's the value you place on your home or business? Do you have insurance for that loss? The next time you walk in, imagine what would happen if someone has sabotaged or stolen you computer. Sure, insurance may cover the physical replacement, but how will you recreate your accounting data? Now, calculate the cost of trying to recreate all of the lost data on your computer - if it can even be done, and compare that to the small cost of doing routine backups.
In the final analysis, the owner of the computer has the responsibility for assuring that backups are done - in a timely manner, run properly, are done on good media, cover all of the desired files, are able to be restored, and are stored in a safe place. Employees may be assigned to do routine elements of the backups, but it's not their data. Computer service firms only assure that the backup is working at a point in time, but, unless they are under specific contract, are not responsible for the continuing correct operation of the backup. If you want someone other than yourself - employee or outside firm - to be responsible for the continuing backup of your computer data, you must write a detailed agreement defining the backup procedures you desire, detailing the various areas of responsibility, and defining specific penalties in case of non-performance. Otherwise, be prepared to accept the responsibility yourself, when - not if - something goes wrong.
The three main storage media used for routine backups are tape cartridge, removable disk, and floppy diskette.
The advantages of tape cartridge backup are the low cost of the tape drive and tape cartridges, availability of good software, ease of use (put all of the contents of a hard drive on a single cartridge), while the disadvantages include reliability of the tape drive and tape cartridges, and the time required.
The advantages of removable media include speed and reliability of restoring data, while the disadvantages include the high cost of the drive and the media, and the limited storage space as compared to the size of most hard drives.
The advantages of floppy diskettes include the low cost of the media and the reliability of restoring data, while the disadvantages include the physical effort required to change and label the diskettes and the amount of time required to do the backup.
The advantages of an on-line service is that the backup is always safe off-site, while the disadvantages include cost, having a backup of only data, and normally having to leave the computer on overnight.
In most situations, our recommendation is for a tape drive unit that can store as much data on a cartridge, in compressed form, as the size of the hard drive. If money is no object, then a removable media solution is the best. If money is limited, then a floppy diskette backup, with the data being compressed, is better then no backup at all.
Backup types normally refer to those done by tape backup software, but can be used with any type of backup. They refer to the status of the file's archive bit, what files are backed up, and how the archive bit is set after the backup. The file archive bit is part of the directory entry for each file on the hard drive, and is turned on by the operating system every time the file is modified.
A FULL backup is one where all files on a logical drive are backed up, regardless of the status of the file's archive bit. After the backup is complete, the archive bit of every file is turned off.
An INCREMENTAL backup is one where each file on a logical drive, whose archive bit is on, is backed up. After the backup is complete, the archive bit of each file backup up is turned off.
A DIFFERENTIAL backup is the same as an incremental, except the archive bit of the backed up files IS NOT reset. Therefore when a differential backup is done after a full backup, all files that have been modified SINCE THE LAST FULL BACKUP are backed up.
A ONE TIME backup may or may not reset the archive bit.
In a perfect world, each file, after being modified, would be backed up. So much for that. We recommend a full backup once a week. Then, to assure safety for each days work, an incremental backup every day, appended to a separate backup tape, should be made. An incremental backup takes less time, and may give more snapshots of a specific file (I want Tuesday's version, not Thursday's). Each week, after the full backup is run, the incremental backup tape can then be erased. A good schedule is to run the full backup on Friday night. If time or media considerations preclude backing up all of the files for the full backup, it can be set up so as to backup only specific directories or individual files. Remember however, that if you don't have all of the files on the backup, recreation after a catastrophic failure will be that much more difficult.
If you do not backup your computer data on a fixed schedule, you are not doing a backup, you are "Data Gambling". You are betting that you will save a copy of your files just before you need it. And when was the last time you won in Las Vegas? And did you win the last ten times you gambled? Establish a routine schedule for doing full backups - every week, two weeks, a month. And then stick to it. The frequency is much less important than the habit. Then do incremental or differential backups between the full backups - preferably daily. Doing an automatic backup every night is a good way to get into a routine. Don't gamble with your data - it's worth too much.
Son, Father, and Grandfather are used to signify the generation of the backup. The SON backup is the most recent, while the FATHER backup preceded the most recent backup, and the GRANDFATHER backup preceded both of them. In general, it is best to keep at least three generations of backups. Advantages for having at least three backups include reliability of restoring files (if the SON backup is bad for some reason, you still have two more chances to retrieve data) and the ability to restore a file that might have already been bad when it was last backed up.
Normal Windows applications usually want to install themselves on logical drive C, even if you have additional logical drives defined. Additionally, many applications set up their data storage either within the same folder (sub-directory) as the program itself, or in a sub-directory off of the program's directory. We recommend partitioning any physical hard drive larger than 512MB into at least two logical partitions; then reserving logical drive C for the operating system, and placing all applications on the other logical drives. For ease of data organization, as well as for backup purposes, it makes sense to either set up a separate logical drive in which data will be stored, or a separate directory, on the same logical drive. With this setup, you need to backup only the data area on a continuing basis, and backup the program area on a less frequent basis. The advantages of this approach are better organization of the files on your hard drive and the decreased amount of backup time required while the disadvantages include a more complex restore of the full contents of the hard drive and the chance that the data you need might have been with the program files and thus not recently backed up.
Our recommendation is to size your tape drive capacity such that you can store all the information on your hard drive on a single tape cartridge, in a compressed form. Most tape drives and cartridges quote storage capacity assuming compression. The software will usually allow for multiple tape cartridges to be used for a single backup. However, the problem with this is that if any physical damage occurs to ANY of the tape cartridges of a backup set, the whole backup is normally lost. A better procedure, if the backup will not fit onto a single tape cartridge, is to break the backup into two or more data sets - select only enough files that will fit on one tape; then, after that backup is done, change tape cartridges and backup the remaining files to the second. In this manner, if physical damage occurs to one tape, at least the files on the other tape can be retrieved.
If you have sized your hard drive and tape drive properly, initially your backup should take less than half of the tape cartridge's storage capacity. This means that more than one backup can be placed on a single tape. The only caution to using this procedure is that if anything physically goes wrong with the tape cartridge, all of the backups on the tape can, and probably will, be lost. Therefore, no matter how many backups are put on the tape cartridge, save at least the last tape cartridge also.
Most backup programs have several options on how the backup catalogs are stored and when they are erased. For the highest reliability, the option where a copy of the catalog is added to the backup tape should be selected. If you also store the catalog on hard disk, you should specify that the hard disk catalog is erased when the tape is erased. Also, you should periodically check to see if there are old catalogs on the hard drive and delete them, since these may take up several megabytes of storage each.
Most backup software packages have some sort of reporting capabilities. This option should be enabled to at least report all errors. The report should be viewed after each backup, to assure proper operation of the backup. There's nothing worse than wanting to use a backed up file, and finding out that no backups have occurred for the past month.
Most backup software programs have an option to read the tape after the backup is completed, and to compare what was written on the backup with what is on the hard drive. This option will more than double the time required to do the backup. If you elect not to use this compare option on a routine basis, you should at least do it once in a while, just to make certain that all is right with the backup software, the tape drive, and the cartridge. You don't even need to run the full compare - just start the compare, let it compare 5-10% of the files and see if there are any errors.
No matter if you run compare every time you run a backup, you should still check once in a while that you can restore a file from a backup tape. This will assure that your procedures are correct, and familiarize you with the restoration process. The best method is to first select a file to test. Next, rename the file on your hard drive, so that you don't lose it if the restore fails (we wouldn't be testing if that couldn't happen, would we?). Now restore the file from the backup tape cartridge, and finally run the application that uses that file. Simple, wasn't it? And now, don't you have a much higher comfort level?
In case of fire, flood, or theft, a backup copy should be kept off-site, or in a safe place. Using a small safe can provide protection against the major loss of a backup - fire. The best procedure, if you are using three generations of backup, is to place the most recent copy off-site. Then, when that copy is needed again for the current backup, replace it with the current most recent backup.
Our experience over the years has been primarily with Colorado Memories (now Hewlett-Packard) and Iomega Travan tape drives. The most dependable, by far, have been the Iomega drives, especially the 2GB external (the internal version requires a 1MB floppy disk transfer rate, which most motherboards do not support or an interface card of it's own, which adds to the cost) and the 3.2GB internal (which will also support 4.4GB extended length tape cartridges). An internal tape drive is the best solution for a single computer or networked computers, while an external drive, although providing a slower data transfer rate, may be best if your backup needs are for several non-networked desktop or laptop computers. The software supplied with these drives, originally written by Arcadia, is excellent, as is that from Seagate. The software included with Windows 95 can be used, but is very limited in its features and capabilities.
Particulate matter will build up, over time, on both the tape head and drive wheel - which moves the tape across the head. A dirty head will cause data to be mis-written and mis-read. A dirty drive wheel can cause tape speed to vary, and lead to data that cannot be read back properly. Following the instructions of the tape drive manufacturer, the tape drive should be cleaned on a routine basis, such as once a month.
If the number of correctable errors on a backup tape starts to increase over time, it might be time to reformat the backup tape cartridge, or, it that doesn't help, replace the tape. Regardless, it's a good habit to reformat your tape cartridges every year or so. The best way to do this is to first use a bulk tape eraser (Radio Shack is good source). This will assure a completely blank tape and normally will save much of the reformatting time. Then, just use your backup software to format the cartridge - this can be a time consuming process, so you might want to schedule it for overnight.
Many times, before critical data changes, a data set can be copied to a backup directory on your hard drive. First, create a backup directory off of the data directory. You might want to name this directory with the date, in the form of YYMMDD, to allow for multiple backups and quick identification of when the backup was done. Now, copy the data files from the data directory to the backup directory. Using this procedure, for example on accounting data before end-of-month posting, it's only a matter of minutes to restore the data if something goes wrong.