Hard Disk Drive, Optical Storage Disks and RAID—Development of Computer Storage System
RAID Recovery - Hard Disk Drive, Optical Storage Disks and RAID—Development of Computer Storage System
Part 1:
Hard disk drive: Hard disk drive is the common storage option that almost all PC possess. After 1990, the development of hard disk soared up. Gradually, two main types of hard disks came into existence evolving from this conventional hard disk: Magnetic Hard Disks and Solid State Disks. But in comparison to these main types of disks, hard disk is preferred to be more suitable storage option for personal computer.
1. Magnetic Hard Disks: It is a digital data storage device that does both read as well as write data through magnetization changes of a magnetic storage disk and includes one or more haphazardly accessible rotatable storage media. In recent market, magnetic hard disks are available with the storage of up to terabytes. In 1956, IBM introduced the very first commercial magnetic HDD with 5MB storage and Hitachi launched 1TB magnetic HDD in last year. Almost 50 years later in 2008, Seagate launched 1.5 TB HDD with 16 to 20 Mb/s transfer rate for personal computer.
2. Solid State Disks: The design of Solid-state disk begins with unifying the Flash memory, Memory controller, RAM controller, RAM, processor and Hosts etc. In 1995, M-Systems launched first flash based solid-state drives which started broadening its horizon. From that very time, the growing importance of flash based SSD flourished across military and aerospace industries. In recent times to enhance the performance, in SSD, RAM is used as a temporary storage and Flash as a permanent storage between processor and flash.
As it does not require much power or any moving parts, it is suitable for hand held systems. This year, Samsung announced 256 GB, 2.5-inch super fast solid-state drive, Toshiba has also launched 3 MLC flash SSD families with SATA interfaces and Supper Talent has also introduced thinnest 256 GB 2.5-inch SSD drive.
Part 2:
Optical Storage Disks: It is not for primary storage. The key applications of optical storage disks are content, back up as well as archiving and its capacity ranges from 300 MB to 30 GB. Before its progression and modification, the Magnetic floppy disks were popular for wide range of small storages. But the Optical disks took over the floppy because of its small storage capacity and short period of life. There are four major commercial types of optical disks:
- Compact Disk
- Laser Disks
- Blu-Ray Disks
- Digital Versatile Disks
1. Compact Disks: Compact disk is the most common form of optical storage. In course of time, some more powerful optical media were developed but CD remained popular for various industries to package software, music, games and movies because of some significant facilities like low-cost, accessibility for back-up as well as physical transfer of data file. It is generally available in CD-R and CD-RW.
2. Laser disks: Laser disk was the first Optical Storage medium used for commercial purposes, especially for movie industry. In 1958, Paul Gregg used the laserdisc technology which later developed and became popular in 80’s for audio songs. Later it was taken over by VHS cassettes and CD/DVD format. In course of time, popularity of Laserdisc has become fade but some users haven’t given up using it.
3. Blu-Ray Disks: Blu-Ray disk is regarded as the future generation of optical disks and capable of keeping high-definition video as well as high density storage. A single sized Blu-ray can contain 25 GB of storage. There is no difference between its size and CD or DVD, but it offers superior transfer rate to CD and DVD. It is commonly used for Game storage.
4. Digital versatile Disks: A digital versatile disk, known as DVD, is a developed form of compact disk and unlike CD, it contains both CD-R and CD-RW. Generally, a standard sized DVD has 4.7 GB/ 8.5 GB storage. Their own specialised applications have differentiated CD from DVD while in the DVD writer one can read/write CDs; on the contrary, CD writer cannot read the DVD.
Part 3:
RAID: RAID (Redundant array of Inexpensive disks) is the modern technology which employs multiple hard disks concurrently to meet the needs of advanced system for application such as highest performance rate, protection against data loss and greater reliability as well as recoverability. It distributes data across several disks to make data accessible even after single disk failure. Three major different types of RAID concepts are Software RAID, Hardware RAID and Firmware/driver based RAID.
Tape Storage: Main usage of tape storage is for offline storage and initiating backup for primary storage, the magnetic tape has been used for data storage for over 50 years during which some major administrative developments evolved in tape formulation, packaging and data density. Modern magnetic tape is packaged in cartridges and cassettes. Tape drive is connected to a computer with SCSI and Fibre channel, FICON, ESCON, SATA, USB, and parallel port etc. It has some specific advantages: it is portable, offers lowest cost per megabyte of all storage media options and per cartridge it provides high capacity. With significant benefits, some limitations are observable:
1. Read/write operation is slow
2. In comparison to other storage media it has short operational life.
Today, tape storage, a sequential access medium, is widely used to store data.
Network Attached Storage: NAS, a hard disk storage system including RAID configuration, is popularly used as a server for big enterprise storage manageability. It is an alternative to a specializes storage area network of SAN, where devices use the block-based SCSI protocol over dedicated internet Protocol network or Fibre channel. It is preferably used for its cost effectiveness with fast data accessibility. Advantages are
1. NAS has very easy installation process
2. Files can easily be shared among several users without reducing the performance rate.
3. Multiple file servers can be merged into one managed storage pool
4. Users are capable of retrieving files from various locations
Storage Area Network:
SAN is a type of local area network specifically designed and dedicated to handle transporting data for storage and retrieval. SAN actually helps storing data either on disks directly connected to server or Network Attached Storage (NAS) devices. Both SAN as well as NAS are used as server storage but the key difference is that NAS uses LAN but SAN does not. The noticeable benefits of SAN over NAS are:
1. SAN offers superior performance than NAS
2. It is highly scalable and has flexibility in configuration
3. It hardly impact on production operation while it allows backup of storage devices.
