On 4/10/11 3:56 PM, Jack wrote: > A lot of Internet vendor websites, such as NewEgg, just may prove > you wrong. Every time I look at NewEgg and others, the "latest- > and-greatest" hard disk has a price premium far WORSE than buying > 2 hard disks of 1/2 the size. Most people don't buy the latest and greatest, the thing to compare is the commodity disk prices, not the cutting edge. Going with your newegg example, and picking 1 & 2TB 3.5" drives: 0.5TB - Hitachi & Seagate & WD $40, Samsung $50 1TB - Hatachi $55, Samsung $60, Seagate & WD $65 2TB - Samsung & Hitachi $80, WD & Seagate $90
>> <http://www.anandtech.com/Show/Index/2888> >> "One estimate for 4K sector technology puts this at 100 bytes of ECC >> data needed for a 4K sector, versus 320 (40x8) for 8 512B sectors. >> Furthermore the larger sectors means that larger erroneous chunks of >> data can be corrected (burst error correction), something that was >> becoming harder as greater areal densities made it easier to wipe out >> larger parts of a 512B sector. As a result, the need for the larger >> sector is born." > Absolutely UNBELIEVABLE!! 40-byte ECCs needed for 512-byte sectors?? > > From 1976-1978 I worked for a company that made hard-disk controllers, > used on PDP-11 systems to control 80- to 300-MB "washing machine" size > disk drives, all they had 35 years ago. Our controller used a 56-bit > ECC, i.e. 7 bytes, to detect all errors and correct bursts of up to 11 > bits. 35 years ago, PDP-11 drivers (I wrote them, too) did not have, > and didn't need, any better error-correction than that, since the disk > drives WORKED! Nor (that I know of) were there "spare sectors", etc. Maybe I'm missing something here, but... (AND BIG DISCLAIMER - I did quick Googling with even quicker Google calc to get the #s below, I may have made very significant math errors) The earliest spinning disks had an areal density of around 2kb/sq. in, the current drives are around 500Gb/sq. in. That means that the size of one bit on the earliest disks was 262,144,000 times as large as a bit on a modern disk. So yes, when looking at a space that is 262 Million times larger, there is a lot more room for error than modern disks, thus a need for much larger ECCs. So, on the original spinning disk a 512b sector "consumed" 0.256 sq. in. On the newest disks that same sector is about 9.5 × 10-10 sq inches, or 0.024 nanometers. Given that the average virus is around 75nm, one virus particle sized damage to the HDD would take out over 3000 512b sectors, on the original disk it would have taken damage of an area equal to nearly 90,000 virus-particles to wipe out ONE 512b sector. So, I don't see that the large ECC is any indication of a lower quality of drive, it is a natural solution to approaching the physics limitation of magnetic recording. ------------------------------------------------------------------------------ Xperia(TM) PLAY It's a major breakthrough. An authentic gaming smartphone on the nation's most reliable network. And it wants your games. http://p.sf.net/sfu/verizon-sfdev _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
