Hard disk drive
General
Typical hard disk drives (HDD) come in various sizes (1.8", 2.5", 3.5") and speeds (4200 - 7200 rpm). There is always one in the computer, but a second HDD can be also external through USB 1.1, USB 2.0, Firewire or SATA. External HDDs are mostly used as fast backup, because with USB 2.0, SATA and Firewire the data transfer rate comes close to that of an internal HDD.
Apart from the typical ATA-disk, there are SCSI-drives (speeds 10- 15000 rpm, transfer 40 Mb/s and higher) and Solid-state-disks(SDD). The latter feature SDRAM memory. In professional versions they have a SCSI interface, power backup and conventional backup ATA-disk, but there are also popular versions that fit the PCI-slot. Here we will only discuss ATA-disks.
Protocol
IDE Bus (Integrated Drive Electronics) is the most common low-cost interface for Hard Disk Drives (HDD), CD-ROMs, DVD-ROMs, etc.. The official specification for the IDE interface is ATA (AT Attachment). Depending on maximum transfer speed that is supported (in MB/s= Mbytes/s ) we distinguish ATA/33, ATA/66, ATA/100 and ATA/133.
Performance parameters
Functional characteristics that PC manufacturers show in their folders are maximum transfer speed, storage capacity and (sometimes) access time (10-20 milliseconds). In consumer tests, the data transfer rates are also tested.
Energy consumption
Presently, 3.5" HDD's use around 5-10 W during read/write, depending also on speed. The 2.5" versions use less than 2-2.5W and as external hard disk don't need an external power supply with USB (max. 500 mAh/ 5V). The operating hours of the HDD depend very much on the type of use. In the BatteryMark test for a P-4 laptop the 2.5" HDD used on average 1.2 W during typical Windows operation. A typical 3.5" might use twice as much (2.4 W). Taking the latter as the typical standard practice in 2000, the energy that can be attributed to a HDD is about 14-15 kWh/PC/yr (at 600 hrs. of annual use).
Courtesy of the French Energy Agency ADEME, Future Electronics project.
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