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Harddisk Density vs Data Retention Time ???
Question:
Does the Data Retention Time of a magnetic harddisk decrease as it's magnetic density increases ?!? My hypothesis would be: the higher the density, the smaller the magnets, the weaker the magnetic field thus faster data loss ?!? Thoughts ? Bye, Skybuck. |
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Harddisk Density vs Data Retention Time ???
skybuck2000 wrote:
Question: Does the Data Retention Time of a magnetic harddisk decrease as it's magnetic density increases ?!? My hypothesis would be: the higher the density, the smaller the magnets, the weaker the magnetic field thus faster data loss ?!? Thoughts ? Bye, Skybuck. Data storage is three-dimensional, not two-dimensional. This is why vertical recording is every bit as good as longitudinal recording (the original method). Vertical recording uses a "backing plate" which is buried below the surface plating. This completes the magnetic circuit and the plate functions as a "holder", amongst other things. Longitudinal recording did not need this, because the flux pointed in a different direction. The platters can be made from non-ferrous materials. The platters could be aluminum or glass. With glass currently being preferred for, say, 18TB drives with nine platters. The glass can be made thinner, which allows the head stack to contain more platters for the ~1" height of the drive. Then, a complicated series of plated-up layers, established the environment the recorded bits will live in. For the digital bits, the platter material is irrelevant to their operation. If the manufacturers are honest about their work, they place some information in the web pages, indicating that some properties were harder to meet than others. For example, perpendicular recording drives might have been slightly more susceptible to externally applied magnetic fields. But the manufacturer claimed they "changed something in the design, to make the new drives resist external magnets, just as well as previous drives". They do attempt to get equal performance from the drives. Except when they outright lie, such as SMR and "how wonderful they are". Third parties have to rub their noses in it, before they will admit they should have been more honest about how poor SMR drives are. And sticking SMR in low-end drives, was just as shabby a business plan, as we would expect from businesses. Even when there was not particularly a need to do it. They were doing stuff like that because "our shareholders appreciate it, when we make crap". In some cases, at the density point in question, there was little to be gained by doing it, except as a mechanism to collect field failure data for future designs. That's about the only excuse I can find. For example, one drive was able to remove one platter, whereas the previous drive was "almost perfect for consumers", since it held up well and did not seem to be crap. (The platters might well have been cheaper to make, as they were not density limited.) A poster in the WinXP group was buying those, for as long as he could get them. Paul |
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Harddisk Density vs Data Retention Time ???
On Tue, 23 Feb 2021 17:57:20 -0800 (PST), skybuck2000
wrote: Question: Does the Data Retention Time of a magnetic harddisk decrease as it's magnetic density increases ?!? My hypothesis would be: the higher the density, the smaller the magnets, the weaker the magnetic field thus faster data loss ?!? Thoughts ? Bye, Skybuck. Flux and permeability. http://hyperphysics.gsu.edu/hbase/Solids/ferro.html#c3 |
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