HARD DRIVE
https://letsknowaboutcomputer.blogspot.com/2011/10/hard-drive.html
Speed
Your computer's central processing unit (CPU) spends a lot of time waiting for your much slower hard drive to catch up. While operations inside the CPU are timed in nanoseconds (one billionth of a second), your hard drive operations are limited to mere milliseconds.
So when you're loading your favorite word processor, for example, your CPU will have to wait until your hard drive can access all of the necessary data and load it into RAM (which also operates in nanoseconds).
Inside
components are the platters and the read/write heads.The platters are disc-shaped, usually made out of aluminum or glass. Unlike the flexible media in floppy diskettes.Hard drives contain multiple platters with two sides each, where data is stored.For every platter, there is a read/write head, all of which move across the discs at the same time since they are all connected to one arm.
Physically, the operation of a hard drive is similar to a floppy diskette drive: the discs spin while the heads move over them to store or read data in tracks and sectors.
If a sufficiently large shock were to be applied to the drive while under power, the force could be enough to cause the heads to go crashing into the spinning platters and once again causing physical damage to the drive, not to mention data loss. This is know as a "head crash.
The average seek time of the drive is the amount of time it takes for the heads to move from one cylinder on the drive to any other cylinder.
Latency is defined as the average time (in milliseconds) that it takes for a sector to be available after the heads have reached a track.The average access time, takes into account the drive's latency.
The maximum transfer rate
Transfer rates come in two different flavors: a disk transfer rate, and a host transfer rate.
The disk transfer rate represent the speed at which data is moved to and from the drive. The disk transfer rate of a drive depends on the spin rate of the drive. A drive with a spin rate of 5400 RPMs will outperform a similar drive at 4500 RPMs.
A combination of a low average access time and high spin rate
is a sign of a drive that will deliver maximum performance.
Partitions
Every file you store on a hard drive relies on some kind of file addressing system to organize all your data. Among PC's, the most common file system is known as FAT (File Allocation System). Windows 95 uses a modified version of FAT called VFAT (virtual FAT), which adds support for long filenames. Windows NT supports both FAT, and its own NTFS format. NTFS is the most advanced file system. It allows access to partitions up to 16 PB (petabyte) in size. [ Equal 16 million terabytes - 16 followed by 18 zeroes).]
Each file system must organize data into segments called clusters.
Microsoft later created FAT32 to support partitions larger than two gigabytes and pathnames greater that 256 characters. It also allows more efficient use of disk space since clusters are four kilobytes rather than 32 kilobytes.
NTFS
NTFS supersedes the FAT file system as the preferred file system for Microsoft’s Windows operating systems. NTFS has several improvements over FAT and HPFS (High Performance File System) such as improved support for metadata and the use of advanced data structures to improve performance, reliability, and disk space utilization, plus additional extensions such as security access control lists (ACL) and file system journaling.
Solid-state drive
A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data. An SSD emulates a hard disk drive interface, thus easily replacing it in most applications. An SSD using SRAM or DRAM (instead of flash memory) is often called a RAM-drive.
