SSD vs. rotational hard drives

Rotational hard drives include hard drives of various form-factors, vendors, and characteristics. The information on these drives is stored through magnetization which upon read request is transformed into a set of bits. The magnetized spot of the disk surface is read as 1, while non-magnetized spot produces 0.

SSD, short for Solid State Drive, is a flash-memory based storage device in which data is stored in bits as well but now 1 and 0 are the result of voltage in cells instead of surface magnetization in a rotational hard drive.

Let’s compare these storage devices by different criteria.

Form-factor

Usually 3.5″, 2.5″, and 1.8″ hard disks are used. Typical memory cards are usually produced in smaller form-factors. Earlier, IBM produced a miniature 1-inch hard drive (IBM Microdrive) in a form-factor of CompactFlash, but now such drives are no longer produced having been surpassed by SSD in performance, capacity, and price per gigabyte.

Flash-based storage device can be produced in a very small form-factor by sacrificing capacity. It is not possible to produce a small hard drive because small mechanical components are difficult to manufacture. That is why modern mobile devices use a flash-memory based storage rather than hard drive.

Access time

Access time is one of the main storage device characteristics. It shows how long it takes for a device to return the first sector of requested data. The shorter the time, the faster the device and all applications respectively. With a hard drive, access time consists of seek time, rotational delay, and transfer time. SSD access time is almost negligible as compared to a hard drive since seek time and rotational delay don’t apply to SSD at all while SSD transfer time is about 0.2 ms. The screenshots of SSD and rotational hard drive benchmark are shown below.

SSD benchmark

SSD

HDD benchmark

HHD

As you can see, access time for a rotational hard drive is approximately 14 ms which is noticeably worse than the SSD access time.

Linear read speed

Linear read speed is another important storage device characteristic. Linear speed of a hard drive is one-quarter of SSD linear speed but nevertheless such a speed is pretty good for any desktop applications. In practice, modern operating system can significantly improve the apparent responsiveness due to caching given that there is enough memory (RAM) on the system. Despite benchmark shows the significant difference (see the blue line in the illustration above), in real life you don’t notice any difference provided that the PC has enough RAM.

Shock resistance

With storage devices, shock resistance mainly implies resistance to vibrations and shock e.g. when using the device in a car.

An SSD is more shock-resistant as opposed to a hard drive, especially in working state. To be precise, SSD is equally shock-resistant both on and off while hard drive shock resistance is different depending on the state of the drive.

Power consumption

SSD consumes significantly less power than a hard drive does. This is mainly because SSD switches between working (high consumption) and sleeping (low consumption) states much faster and consumes less power than hard drive. Mechanical hard drive on awakening has to spin up spending several seconds and consuming quite a lot of electricity. That is why a hard drive usually doesn’t power off immediately but instead waits for a few minutes (downtime) because the on-off cycle is time-and-energy consuming. SSD switches between on and off states instantly, not requiring additional electricity.

Capacity

Usually, SSD capacity is less than hard drive capacity. As of 2013, according to the newegg.com site, a 1TB SSD costs about $1500 while the price of a regular hard drive of the same capacity is about $80.

Recoverability of data

One more difference is that SSD can write data only to zero-filled cells. This SSD specific led to the TRIM command which cleans cells with unused data when SSD is idle. All this significantly decreases the chances to recover deleted data from an SSD. With a hard drive, unless sectors with previous data are needed to write new files, data is not erased. With an SSD, even if you write nothing to it, SSD still erases unnecessary data in advance.

To upgrade to an SSD or not?

Upgrading to an SSD is worthwhile if a system lacks memory and therefore no memory is available for caching. Additionally, you get noticeable advantage with an SSD if you due to some reason work with a lot of small files or with virtual machines.

Alternatively, you can just add RAM (if possible) and get the same effect as in case of replacing hard drive with an SSD. You immediately observe the effect of a transition from 4 GB RAM to 8 GB, from 8 GB to 16 GB – so-so, and you don’t notice the difference at all if you upgrade the RAM up to more than 16 GB.

In desktop PCs, where resistance to vibrations and power consumption are of little importance (as long as you do not use a RAID array, say, of five disks), upgrading to an SSD is unnecessary particularly in terms of price per gigabyte.

Also, before you consider an upgrade to SSD to improve gaming performance, you should check your video card to ensure that it is not the bottleneck.

About Elena Pakhomova

Elena Pakhomova is a co-founder of ReclaiMe data recovery software company. In addition to her main activities, she contributes to various technology outlets. Read her blog at www.data-recovery-weekly.blogspot.com

Additional Resources

Comments

  1. Thanks for SSD. Love it!
    This is very useful specially for me who is on the online business,

  2. Data speed is awesome but recoverability is an issue unless features were impressive. Those who want to use it then they definitely need a software for data protection and recovery..

  3. SSD is the best! Very useful in every aspect of online business.
    Thanks for sharing this.

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