Data storage systems have been around since the 1920’s with the invention of the magnetic tape, since then we have seen, how data storage systems have evolved into something we know today as cloud computing. Some of the types of storage used today are: magnetic hard disk drives (HDD), optical storage, floppy disk, solid state storage (SSD), memory, RAID, thumb drive and external hard drives, macromolecular data storage. These types of data storage systems are known as secondary storage devices, because the CPU does not have direct access to these storage devices, except for memory.
The Magnetic Hard Disk Drive or HDD: This type of storage device has been the primary storage device, for computers for more than five decades.
- Size: The capacity and performance of the magnetic hard disk drives, are its primary characteristics, as of today the capacity of a HDD is about one-terabyte (TB), which is 1000 gigabytes (GB). The HDD stores data, due to its magnetic platters, which are divided into billions of tiny areas, where each of them, can be used to store data, through magnetization (stores a 1) or demagnetization (stores a 0). Computer scientists of course are trying to increase the capacity of the HDD, in order to give user a better experience. In the scientific arena for example, researchers are proposing a replacement for hard disk drives all together, and instead, develop a new method of information storages, which can store petabytes, of data generated by the user in a sugar cub (1 cm3). Hard drives have a storage capacities of 500GB, 750GB, 1, 2+TB.
- Speed: The faster the platters of a HDD spins, the faster the HDD would perform, the performance of an HDD is measured in revolution per minutes or RPM. The typical RPM of a laptop’s HDD is 5400 RPM or 7200 RPM.
- Error handling: In windows there is a command that can be used on the cmd, which is chkdsk, which can be used to check the HDD, because the HDD can run into errors. By separating where the operating system is installed and the user’s home directory on different drives, can also help manage read/write errors. Checking for bad sectors can also help, in testing the health conditions of a magnetic HDD.
- Cost: The cost of the HDD has decreased significantly, in 1981 a HDD would cost around $404,444 per gigabyte, but today that number has dropped to cents per gigabyte.
Optical data storage: This data storage system, use a one dimensional spiral stream, in order to record information. The data stored is retrieved through optical detection, which senses changes in the intensity or polarization that is reflected by a laser beam.
- Size: The storage density of recording media is best described as CD-ROM (compact-disk read-only) and DVDs (digital video disks). CD-ROMs can hold around 700 MB (megabytes), and DVDs can hold around 4.7 GB (gigabytes) and a dual-layered DVD can hold 8.5 GB. Let’s also not forget about Blu-Ray disks, which can hold 25-50 GB and twice that amount on a dual-layer Blu-Ray disc.
- Speed: The X-factor is used to specify optical drive speeds, where CD-ROM drives uses 150 KB/s, referred to as 1X, to transfer data. A max drive of 52X indicated 52 times 150 KB/s or 7,800 KB/s. The X-factor in a DVD is 1.321MB/s which is 1X, it is nine time faster than a 1X CD-ROM drive.
- Error Handling: The detection and correction of typical error patterns, such as scratch and/or pollution, which is a burst error, has to be done by cleaning the disc gently.
- Cost: The cost of CD-ROMs and DVDs have been reduced tremendously over the years, which is at cents per GB.
Solid State Drive (SSD): This type of storage device has similar functionalities, to the hard disk drives (HDDs).
- Size: Samsung unveiled the largest capacity SSD at 2.5-inch, which can hold 15.36TB, at a 2015 summit. Most SSD though have a storage capacity of 32GB, 64GB, 128GB, 256GB, and 512 GB.
- Speed: Performance changes over times, performance is best when the SSD is brand new, then it will stabilize over time, this is known as steady state, which depends on the type and amount of data previously written to the SSD. The I/O request being made will also impact the performance of SSD.
- Error Handling: Controllers are used to extend the life of an SSD, error correction algorithms ensure the data is safely stored. Controllers map bad memory areas and error controllers correct bit errors.
- Cost: The cost of an SSD has decreased tremendously, today an SSD can be purchased for $50.
Redundant Array of Independent Disks or RAID: Many small to medium-sized businesses (SMBs) use this type of storage device, which was created to find a safer way to store data.
- Size: There are levels to RAID such as level 1, 2, 3, 4, 5 and 6 and when these storage levels, are created with disc of different sizes, the smallest disk will dictate how much storage space, can the other discs provide. The size of a RAID will depend on how many disk drives are used, and will be limited to the size of the disk drives.
- Speed: In this type of storage device, the performance of the RAID storage device depends on the type of disc drives, it uses. HDD will not provide the best performance, unless a lot of drives are used, however SSD will increase the performance of a RAID, with fewer resources used.
- Error Handling: A disk drive which has fail, is pointed out by the RAID controller system and marks this drive as unusable, if the drive is not responding. This event is not reliable, because the performance degrades, and the process can take a long time.
- Cost: RAID 1 is very expensive, while RAID 0 is affordable, and RAID 5 is the best price to value storage device available.
Macromolecular data storage: In order to manage biological data a lot of space is required and maybe even a new type of HDD, according to scientists.
- Size: A long macromolecule, which consist of at least two bases, is used in order to store digital information. The capacity of user data a macromolecule can handle is very large and it is measured in petabytes, which is very adequate for biological data, such as DNA.
- Speed: This type of data storage can read/write information at hundreds of megabits/sec.
- Error Handling: Modulation coding and error-correction coding is used to handle errors and to maintain the fidelity of the data.
- Cost: Expect for this type of storage to be very expensive, because it is dealing with biological material.
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Masud Mansuripur, "Advances in macromolecular data storage", Proc. SPIE 9201, Optical Data Storage 2014, 92010A (5 September 2014); doi: 10.1117/12.2060549; http://dx.doi.org/10.1117/12.2060549