Removable storage earlier was for sequential magnetic tapes only but now random-access, solid-state removable storage is prevalent.
Magnetic Tape
It is an older form of removable storage using magnetic tapes to store data for backup. Magnetic tape is a medium for magnetic recording, made of a thin magnetized coating on a long, narrow strip of plastic. Tape backup devices can be installed internally or externally in a chassis. They hold much more data than any other medium but are slow due to sequential access. Tape libraries are used in enterprises and networks for backup as they are the most reliable over the long term.
Tape has historically offered enough advantage in cost over disk storage to make it a viable product, particularly for backup, where media removability is necessary. Tape remains a viable alternative to disk in some situations due to its lower cost per bit. The highest capacity tape media are generally on the same order as the largest available disk drives (about 5 TB in 2011). Modern cartridge formats include LTO, DLT, and DAT/DDC. Tape has the benefit of a long duration during which the media can be guaranteed to retain the data stored on the media. Fifteen (15) to thirty (30) years of archival data storage is cited by manufacturers of modern data tape such as Linear Tape-Open media.
USB DRIVES
It consists of a flash memory data storage device integrated with a USB (Universal Serial Bus) interface. They are removable and rewritable, and physically much smaller to fit in a pocket. Most weigh less than 30 g and can store upto 256 GB and allow 1 million write or erase cycles with a 10-year storage time. They are smaller, faster, have thousands of times more capacity, and are more durable and reliable because of their lack of moving parts. They use the USB mass storage standard, supported natively by modern operating systems like Linux, Mac OS X, and Windows. Nothing moves mechanically in a flash drive for read and write. They are also called USB flash drives or pen drives. A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case which can be carried in a pocket and USB connector may be protected by a removable cap. Most flash drives use a standard type-A USB connection and draw power from the computer via external USB connection. USB 2.0 and upcoming USB 3.0 are available in market. External hard disk also use USB interface as they have the drive, a DC power input and a Type-B USB interface and can be built by user also as the kit is also available in market.
Solid-State Disk Drives (SSD)
It is a data storage device that uses solid-state memory to store data. Hard disk drives (HDDs) are electromechanical devices using disks and read/write heads but SSDs, use microchips to store data in non-volatile memory chips and contain no moving parts. SSDs are less susceptible to physical shock, silent, and have lower access time and latency. SSDs use the same interface as hard disk drives, thus easily replacing them in most applications. Most SSDs use NAND-based flash memory. Every SSD has a controller which has the electronics to bridge the NAND memory components and PC. They are in hard disk form factors which are known by the size of the rotating media, e.g., 5.25″, 3.5″, 2.5″, 1.8″ but form factors common to memory modules are also used by SSDs like PCIe, mini PCIe, mini-DIMM, and may also sit directly on the SATA connector on the motherboard without any other support or mechanical mount. As of February 2011, NAND flash SSDs cost about (US) $1.20–2.00 per GB. SSDs come in different sizes up to 2TB but are typically not larger than 40-120GB. The weight of flash memory and the circuit board material are very light and make no sound.
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