Devices of more than 2 capacity GB
In general we can say that in the world PCs only use in a common way two types of devices of storage that reach this capacity: the tapes of information and the magneto-optic ones of 5,25 ". The tapes are devices faced specially to realize massive safety copies to low cost, while the magneto-optic ones of 5,25 " are much more versatile... and much more expensive.
Information magnetic tapes - even more than 4 GB
It is sure that it has seen more than once in an ancient movie or in the television this species of enormous closets glazed in those that a few dark circles of more than 30 cm in diameter turn like madmen while Sean Connery, personifying the indescribable one 007, faces the crazy shift scientist; good, since these circles are tapes of information of computer.Fortunately the times have changed very much: nowadays the information tapes come with case and they are not major than those of music or the 8 mm videotapes, what is a clear advance; on the other hand, if Pierce Brosnan is so good 007 as Connery there would be opinions, although it it does not harm either.
The information magnetic tapes or streamers they present many problems like device of storage of information: almost all the types are tremendously slow (typically less than 250 Kb/s, an almost ridiculous speed); what is worse, the information are stored sequentially, for what if he wants to recover a file that is to half of the tape will have to wait for several tens seconds until the tape should come to this area; and also, the information is not in excess sure, since like magnetic devices the magnetic fields, the heat affect them, etc, in addition to the proper wear of the tapes.
Then: why are they made? Because they are cheap, very cheap. Units exist readers - tape recorders for less than 15.000 pts, and the tapes can cost approximately 3.000 pts one of 2 GB. But the being sales does not eliminate the rest of problems, therefore they are only practical to realize backups massive of the hard disk (or selective, according to), although bearing in mind that the process for a hard disk of average size can go so far as to last easily a pair of hours using normal tapes.
One of the motives that does so slow to the information tapes is the type of interface that is used. Generally maximum uses the connector for disk drive, which is very slow, the commented ones 250 Kb/s (that rarely is reached); what is more, has to be able to form the BIOS as if we had connected a 2,88 MB disk drive, what is not possible if the BIOS is ancient, like that of any 486 and the previous ones. In case the BIOS admits as maximum 1,44 MB disk drives, the speed will come down to the half.
In other tapes the parallel port is used (with major band, but scarcely well used) and in more expensive and rapid information tapes there are used interfaces EIDE or SCSI, what increases the yield but never of spectacular form, since the element any more limitante is the proper mechanical machinery of the unit. Also, the way of sequential access makes completely impossible to use them of effective form "to the hard disk", unless we understand because of it to wait and to wait whenever we want a file...
The principal types of tape units are the QIC, Travan and DAT. The Travan is a subclass that derives from the QIC, with which they usually keep a certain compatibility grade; both form the economic segment of the storage in tape, for example 20.000 pts a unit of 1 GB of capacity and 2.000 pts each of the corresponding tapes.
The tapes DAT (Digital Audio Covers) are another history, certainly, both in speed and in price. The access keeps on being sequential, but the continuous transference of information (reading or writing) can go so far as to overcome 1 MB/s, what justifies that the practical totality they use interface SCSI. Nevertheless, the price turns out to be prohibitive for not professional use: more than 100.000 pts a unit of 4 capacity GB, although the tapes are cheap: approximately 4.000 pts for one of 4 GB, certainly really small.
Marks and models exist infinity, since it is a market very mature and based mostly on standards, what redounds to a few lower prices and a major facility to find the appropriate tapes. Out-standing examples are the models Ditto de Iomega, the Colorado of Hewlett Packard, TapeStor de Seagate and the models DAT of Sony or Hewlett Packard.
To end, a very important curiosity: the real physical capacity of the tapes of information is usually half of the face-value indicated in the exterior of the box of the unit or of the tape, since to only to be used to do backups, generally compressing the information, they suppose that it goes to reach a compression of 2:1. In fact the compression depends on the type of information to be compressed (the programs compress little and the files of great text, for example), for what I recommend to him to think rather about a compression 1,5:1. Summing up, that if the unit promises to be as of 2 GB, surely that it is of 1 GB (what will come somewhere but in smaller letters) and almost surely that it will be able to store more or less 1,5 GB of compressed information; in this text this advertizing stunt has not been used.
Magneto-optic of 5,25 " - up to 4,6 GB
The magneto-optic ones of 5,25 " base on the same technology as his small brothers of 3,5 ", for what the same advantages hoard: big reliability and durability of the information simultaneously that a speed reasonably high.
In this case, also, the speed becomes even top: more than 3 MB/s in reading and more than 1,5 MB/s in writing using normal discs. If the device supports discs LIMDOW, the writing speed almost doubles, with what we would come at one more speed of 5 times top to the tape recorder of CD-ROMs more rapid and comparable to that of the hard disks, what determines the use of the interface SCSI exclusively and the appellative one of optical hard disks that applies them to itself sometimes.
Also, the change of size of 3,5 " to 5,25 " implies a big capacity increase; the discs go from 650 MB to the 5,2 GB, or what is the same: from the capacity of only one CD - ROM up to that of 8, happening for the most common discs, those of 1,3 and 2,6 GB. With these numbers and this speed, to do a backup of a hard disk of 2,5 GB does not take any more than one quarter of an hour and the proved cartridge is only a little bigger than the case of a CD, since to that the discs look alike: to CDs with a case type diskette.
At present the most widespread models are those of 2,6 GB of maximum capacity, in that the system LIMDOW is implanted quickly. Since it is a question of devices based on standards, there exist several companies that make them, for example Hewlett Packard, Sony or Pinnacle Micro.
The latter company, Pinnacle, who devotes himself almost exclusive to these devices, has one of the most interesting products of this market: the Apex. One treats as a device that admits normal discs of 2,6 GB, but that also has a few special discs, as proprietary design (not compatible with other devices), that the 4,6 come even GB, all this with a big speed and at a price even lower than that of many normal devices of only 2,6 GB.
But this, the price, is the disadvantage (terrible disadvantage) of this type of peripheral. The units of 2,6 GB sell to themselves for approximately 175.000 pts, while those of 5,2 overcome GB loosely this price. The discs, nevertheless, are quite economic for his big capacity, enormous resistance and durability: approximately 10.000 pts one of 2,6 GB. Although if he thinks to buy a device of really massive storage and has enough money, he does not doubt it: better option does not exist, especially if he wants the absolute safety of which in 30 years it will be still able to recover his information without problems.
Safety copies (backups)
On the previous pages one has commented numerous times on the biggest or minor suitability of the devices for his use like safety copy devices or, as say the Englishmen, backup. Next I am going to try to give a few general ideas on this topic, which has a lot of major importance of what seems.
If some day went so far as to publish a computer science manual, probably he will start by saying: "FIRST OF ALL, SUPPORT RECENT BACKUPS OF HIS FILES OF INFORMATION", in capital letters and in the center of the first page. Next he would have to tell what a file, a backup is and especially a computer, but I am afraid that if it will leave the advice for further on it already would not have the force that is deserved.
Do not forget that a computer is only a jumble of cables, plastic and metal, for much that finds it hard to myself to recognize it; it is a machine, and as such it is not especially interesting in itself, but it it is especially for the information that it contains: the letters to the fiancée, the reports of the work, the photos of astronomy, the games, the invoices of the last trimester... This is the important thing, but it seems that we forget it very often; we trust that as it has never broken, it will never break, forgetting the only law of the computer science, the Law of Murphy:
And this way up to the infinite. The hard disks trump little, but more desirable thing; even if they do not fail, they can turn affected by multiple causes, from an increase of electrical tension up to a trip with a cable that makes us throw the computer to the soil. The only solution is to have safety copies, to update them often and to hope that it should never be necessary to us to use them; next I present Ten Orders of the Backups to him: