HDD: Hard Disk Drive By Tyler Beckett Janaki Ramachandran Why Are We Here?
Disks store a lot more info, and they’re much faster; they’re also more precise, because information is stored in much smaller “magnetic domains” than in a tape.
Both use same magnetic method of recording and storage.
The internals of a hard-drive primarily consist of: -A row of platters that spin very fast-A "comb" of heads in between the platters
The industry standard rotational speed today is:7,200 RPMs or approximately 150 MPH.
The old standard was 5,400 RPMs and the fastest consumer hard drives today run up to 15,000 RPMs.
Platters are made from:-Non-magnetic material(usually glass or aluminum)-Coated with a thin layer of magnetic materialGaps of equal size are the data, stored as 1's or 0's via magnetism.
Heads are tiny Read-and-Write magnetic heads, held just above the surface of the fast-spinning disks by an actuator arm (the “comb”).
They detect and modify the magnetism of the area directly below the head.
The actuator arm moves side to side (slightly circular because of the motion) to reach the entire surface of the platter.
The whole head setup runs on a cushion of air created by the air being pushed by the friction between the fast-spinning platters.
This keeps the heads incredibly close to the platters.
Hard drives are mostly airtight, to prevent dust, hair, fingerprints and the like to enter into the very delicate environment inside a hard disk.
The slightest interference of a particle of dust can offset a head and cause it to “crash” into the hard drive, causing even more debris to go flying into the device, resulting in a “hard drive crash.”
A small, highly filtered valve on the outside of the shell is used to regulate the air pressure with that of the surrounding environment.
USB and Firewire are the standard connections for external hard drives today.
Internal Hard drives pretty much all use ATA today, but the trend has been towards SATA and SATA2.
USB2 = 60 MB/s
Firewire 400 = 50 MB/s
ATA = 100 MB/s or 133 MB/s
SATA = 1.5 GB/s
SATA2 = 3 GB/s
RAID stands for Redundant Array of Independent (sometimes Inexpensive) Disks.
RAID 0 - instance mirror-backup (often used by servers and mainframes)
RAID 1 - Striped HDDs (often used by gamers)
RAID 0+1 - Mirrored Striped HDDs(often used by both mainframes and gamers)
RAID 5 - 3-drive parry bit combination (designed to safe check your striped drives)
JBOD - Just a Bunch Of Drives
Capacity – the number of bytes a disk can hold
The capacity of Hard Drives has increased dramatically over the years.