Capacity and access speed:

PC hard disk drive capacity (measured in GB). The vertical axis is logarithmic, so the accurate line corresponds to exponential growth.

 By using  rigid  disks  and  sealing  the  unit  permit  much  tighter  tolerances  than  in  a  floppy  disk  drive. As a result, hard disk drives can store more data than floppy disk drives and may access and transmit it quicker.

• The speediest  -enterprise? HDDs spin at 10,000 or 15,000 rpm, and may gain sequential  media transfer speeds above the 1.6 Gbit/s. and a sustained transfer rate up to 1 Gbit/s. Drives running at 10,000
• A classic "desktop HDD" must store between 120 GB and 2 TB although rarely above 500GB of data
• As of date April 2009, the highest power consumer HDDs is 2 TB.
• (based on US market data rotate at 5,400 to 10,000 rpm, and contain a media transfer rate of 1 Gbit/s or higher. (1 GB = 109 B; 1 Gbit/s = 109 bit/s)or 15,000 rpm use smaller platters to mitigate improved power requirements (as they have less air drag) and therefore usually have lower capacity than the uppermost capacity desktop drives.
• "Mobile HDDs", for example laptop HDDs, that are physically smaller than their enterprise counterparts and desktop, tend to be slower and have lower capacity. A typical mobile HDD spins at 5,400 rpm, having 7,200 rpm models available for a slight price premium. Due to physically smaller platter(s) , mobile HDDs usually have lower capacity than their physically larger counterparts.

The exponential increases in data access speeds of HDDs and disk space and have enabled the commercial viability of consumer products that need large storage capacities, such as digital audio players  and digital video recorders and.

The major way to decrease access time is to amplify rotational speed, so reducing rotational delay, though the major way to increase and storage capacity and throughput is to increase areal density. Based on historic trends, analysts guess a future growth in HDD bit compactness (and therefore capacity) of about 40% per year. Access times have not kept up having throughput increases, which themselves have not kept up with increase in storage capacity.

First 3.5″ HDD marketed as capable to store 1 TB was the Hitachi Desk star 7K1000. It have 5 platters at about 200 GB each, providing 1 TB (935.5 GiB) of usable space; note the dissimilarity among its capacity in decimal units (1 TB = 1012  bytes) and binary units (1 TiB = 1024 GiB = 240  bytes). 

Posted Date: 10/13/2012 6:23:55 AM | Location : United States

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