Solid State Hard Drives And Hard Disk Drives

Two types of devices having similar functions viz. Solid State hard Drives and Hard Disk Drives will be compared in our research work. The primary objective of our research work in this comparative analysis paper is to summarize the merits and demerits of each device. It will be our honest endeavor to present an unbiased analysis without reader's provocation in zeroing into one of the devices.

For a comparative analysis, the overall information relating to Solid State Hard Drives and Hard Disk Drives will be considered.

Solid State Hard Drive (SSD) is the referral term used for data storage. Its primary mechanism of functioning is using solid state memory for storing data in a continuous manner. For its functioning, microchips are used for collecting data in the non-volatile memory chips. [1]

Absence of any moving parts in a SSD is one of important feature. It is resistant to shock, requires shorter time duration for data access besides having lower latency. Data access to an SSD can be made even without it being connected to any power source. The saved information can be obtained through volatile random access memory. Hence, users can access, save and especially work on the data even in the absence of electric power. The System saves in auto mode every changes of the information and builds backup copies in situations where the computer has been powered off for emergency. [2]

Coming to Hard Disk Drive (HDD), it would be useful to start with its origin. IBM invented the HDD and used it in Computers for the first time in 1956 in general purpose computers as a secondary memory device. The primary benefit of the device is its capacity to store data which has sharply increased over the years leading to the growing popularity of its use.

The important principles of the HDD functioning constitutes as follows (i) It has rotating rigid platters with the motor-driven spindle. The entire system is encased in a protective enclosure. The information is read from the disk or written back into the disk by the read/write heads, which move across the film air on the top of the platters. [3]

The HDD has evolved over the years from standalone boxes to the present era's desktop 3.5 inch device that is built into the computer. Besides, presently 2.5 inch drives are available for mobile systems. The high operating speeds of today's HDD on serial interfaces like SATA or SAS is its marked feature. [4]

Presently a cross between HDD and SSD is available in the market known as the hybrid drive which possesses all the positive features of both the drives.

While comparing HDD and SSD, the following features are required to be delineated for a comparative analysis: time required for spin-up for random access to the information, read latency time; consistent reading; defragmentation; acoustic levels and mechanical consistency; resistance towards extreme causes; weight and volume features; possibilities of parallel operations; limitations of software, price, power consumption levels, capacity issues, read and write performance symmetry. [5]

Initially we would consider the physical parameters: the weight and volume of SSD is markedly less compared to a HDD.

As SSD does not have any moving parts, they do not produce any sound and in case of HDD, the level of sound generated by the moving parts- spindle motor heads is dependent on the model of the device. Coming to the latency time i.e. the time needed for basic operations like executing and the device to start working, SSD is faster which doesn't need spin up time since every action is executed instantaneously and needs just a few seconds to initiate working of the device.

The random access time- the SSD needs considerably lesser time (0,1 millisecond) for this operation as the information can be accessed straightaway from the flash memory and in case of HDD it takes is 5 to 10 millisecond for its head to move. The read latency time for a SSD is low since information is required to be fetched from every location; in case of HDD the same is considerably higher due to the presence of mechanical components in its manufacturing and it needs more time for its functioning (moving).

The consistent reading performance in case of an SSD is always the same since it is not dependent on which location of the drive the information is available, while in case of HDD- in case the data is written in a fragmented manner, it would need greater time for the moving head to seek data from different locations of the drive. Due to this HDDs needs frequent defragmentation process when some data have been deleted and re-written.

The mechanical dependability of a SSD is assured by the absence of any moving parts which accounts for its extended life term. The HDD details must be substituted and changed after considerable use of the same. In extreme situations, we encounter similar situation to the above stated mechanical reliability description. Considering accidents like shock, vibration and other erratic and unsurprising events, SSD is the clear choice since it is devoid of any moving parts.

Data in a HDD drive can change or get deleted due to presence of strong magnetic fields which does not happen in case of a SSD.

Due to presence of multiple flash chips in a SSD during manufacturing of the device, read and write instructions can be executed simultaneously. The multiple heads of HDD must be aligned on the same cylinder while executing parallel operations.

Regarding software encryption limitations, SSD possesses low security levels and the NAND Flash memory is unable to be rewritten. On the other hand in a HDD, data can be overwritten on each sector directly.

The ultimate and the most crucial issue happen to be the economical aspect, the power consumption issue and price. As per data available for October 2010, unit price of 1GB SSD ranges from $1.4 to $ 2.0 per GB. However a 1 GB HDD costs $0.1 for 3.5 and $0.2 for 2.5 Drives. [6]

A high performance HDD needs 12-18 watts of power while a laptop HDD requires 2 watts. On the other hand a SSD requires just half to a third of the power consumed by a HDD.

To sum up, it can be stated that a SSD device is a newly developed one. Its developers have considered every limitation of the HDD to launch the SSD with important features as per its primary characteristics and parameters. However, the only hitch is its exorbitant price.

End Notes

[1] STEC. (2010)SSD Power Savings Render Significant Reduction to TCO."

[2]Solid State Storage 101: An introduction to Solid State Storage. SNIA. January 2009.

[3] Magnetic Storage Handbook 2nd Ed., Section 2.1.1, Disk File Technology, Mee and Daniel, (c)1990

[4] "Iterative Detection Read Channel Technology in Hard Disk Drives", Hitachi.

[5] Markoff, John (2008-12-11). ?Computing without whirring drive? The New York Times.


Ocz technology (2010) OCZ Z-Drive R2 p88 PCI-Express SSD. Retrieved from

Hitachi STEC. (2010) "Iterative Detection Read Channel Technology in Hard Disk Drives", SSD Power Savings Render Significant Reduction to TCO.

Solid State Storage 101. (2009). An introduction to Solid State Storage. SNIA. Retrieved from

Mee and Daniel, Markoff, John (2008). Magnetic Storage Handbook 2nd Ed., Section 2.1.1, Disk File Technology, ‘Computing without whirring drive’ The New York Times. Retrieved from

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