The insides of a hard disk drive
In the last issue we covered how to keep your computer running. This is available at http://www.elearnaid.com/cotetikeyoco.html. However, no matter what you do you can not be absolutely assured that your hard disk drive will not fail. In case it does, you need to backup your data. If the electronics of a hard drive fail you might still be able to recover your data; but the more likely failure, is mechanical. In this situation, recovering your data from the hard drive can be difficult and expensive. Disk drives consist of a spindle with layers of platters. The magnetic heads are designed to ride against the platter in a lubricated landing zone on the platter. Once the revolutions of platters get up to the normal speed the air near the surface of the platter causes the head to fly above the platter. At this point, the drive goes into a ready state and the arms swing positioning the heads over the data. The close proximity of the magnetic head to the platter allows high density recording but the possibility of a head crash always exists. If a head crash occurs the heads grind the surface of the platters and only some of your data can be recovered if any at all.
If the potential mechanical failures are not enough there are the viruses and other malicious activity that could cause you to loose your data. Of course, data can be erased due to just plain error. So copies of your data is a vital.
Tapes used to be the method of choice for backing up large amounts of computer data, however, most users can now use DVDs. The advantage of a disc is that you can retrieve your data very fast compared to finding the correct spot on a tape. Double layer DVD backup drives sell for around eighty dollars and can backup up about 8.5 billion bytes (one byte stores one character of text) . However, the Double Layer DVDs are currently expensive and sells for about five dollars a disk for quantity one. Till the price of the media comes down you can back up with single layer CD. You can use 16x speed (22.1 million bytes per second) using single layer DVD and this media is about 60 cents a piece. If you do not need the speed 4x, single layer DVD are about 33 cents each or less. For most users 4x is fast enough and single layer holds enough for daily backups. For 33 cents in media cost you can save your data and keep the copies for a long time in case something turns up missing that has disappeared a while earlier unnoticed from your hard drive. If your backups due not fill up the DVD you can put several days worth of backups on one DVD. You can see that a disk has been used and how much of it has been used just by looking at the reflective side of the DVD. The writing is done from the center out and the part that has been written to is darker. You can and should write what was backed up and when on the top side of the disk but you should use a felt tip pen as the data is stored just below the top layer you are writing on.
For backing up very large quantities of data backing up to multiple DVDs with the DVDs mounted on a carousel might be available in the future but for now tapes are still used.
There are a number of choices of software for backing up to DVD. Most of the software compresses the data and creates an image of the data on your hard drive and then writes it to the disk. I found software that is easy to use and fast because it compresses the data and then writes it directly to the DVD. The software is called CyberLink Power Backup. I have used it to backup and restore individual files and it works just fine. The program allows you to create scheduled backup jobs. There is a free thirty day trail available at http://www.gocyberlink.com/multi/download/download.jsp
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