Solid State Drives vs. Hard Disk Drives (SSD vs HDD)

Solid state drives (SSD) are data storage devices that used to store persistent data. In terms of function SSD's serve the same purpose as your typical hard disk drive (HDD), but are much faster than your typical hard drive. The main difference between solid state drives and hard disk drives is that hard disk drives are electromechanical, meaning that they have moving parts. In a HDD the hard drive has an actual magnetic disk that needs to spin and it has a moving read/write head. So hard disk drives are slower because they need to wait for these moving parts to get into place before they can save information to the hard drive or before then can read files. In contrast, solid state drives have no moving parts and they store information in microchips, much like a USB flash drive (but much faster!) and they can instantly start saving information or reading files, without having to wait for any moving parts to get in place.

Solid State Drive (SSD) Pro's and Benefits

Solid state drives have no spin up time, meaning they are instantly ready to read or write to the drive, while HDD's may need up to around 2 seconds before they can actually access the drive. Solid state drives are also able to both read and write files at about twice the speeds of hard disk drives. This means your computer will boot faster and video games and other programs will load quicker! SSD's also do not need to be defragmented, in contrast a fragmented HDD will greatly reduce read/write times of the hard disk drives and slow your computer down. SSD's are also much less likely to break if you drop them or if they sustain an impact, because they have no moving parts. Strong magnetic fields can corrupt an HDD, while the SSD's are unaffected by magnets. Solid state drives also consume much less power and produce much less heat than hard disk drives do (2W SDD vs 7W HDD power consumption).

Solid State Drive (SSD) Cons

The only two current cons to having a solid state drive is if you need to encrypt data or you don't want to fork out the extra cash to buy one. Currently the most popular SSD are based on MLC NAND flash memory and this type of memory cannot overwrite files and can only write information to empty blocks or previously erased blocks. This means that if you have a file on your computer and you use a program to encrypt it, the old data is not overwritten and can still be accessed. Thus you would need to encrypt the file, and then securely erase the old data, preferably with a secure erase feature built into the SSD. If you need to encrypt data I highly recommend buying a SSD that has a "Secure Erase" feature built into the drive or look into Truecrypt creating an entire encrypted partition of the drive and Windows installation. Solid state drives are currently much more expensive than HDD's. Currently a SSD costs about $1.80 USD per gigabyte, while a HDD costs about $0.11 USD per gigabyte (As of 3/17/2011).

Solid State Drive (SSD) Lifespan

SSD also has a limited life span due to the limited number of write cycles. However, today's current MLC SSD's have an Mean time between failures (MTBF) of 2,000,000 hours, which simply put means that your SSD will typically last for 228 years! They technically have a limited amount of writes they can perform too, but they are able to sustain about 40 years of constant, non-stop, writing before they would start failing. Hopefully that puts the myth that SSD's will not last very long to rest, unless you need to have your SSD last you for over 228 years...

The table below gives a pretty good compare and contrast between HDD vs SSD.

HDD vs SSD
Characteristic	Hard Disk Drive (HDD)	Solid State Drive (SSD)
Sensitive to Magnets	Magnets will alter or destroy data	Magnets have no effect on data
Power Consumption	7 Watt average	2 Watt average
Time to Spin Up	Up to 2 seconds before HDD can read/write to drive	Instantaneous, able to read/write immediately
Read Speed (SATA)	Roughly 100MB/s, can very depending on level of fragmentation	250 MB/s
Write Speed (SATA)	50-70 MB/s, can very depending on level of fragmentation. Up to 118 MB/s on HDD's such as the WD Velociraptor.	200-250MB/s.
Lifespan	May fail due to vibrations or impact, usual MTBF of 1,500,000 hours (171 years) No finite number of writes	MTBF of 2,000,000 hours, AKA 228 years. Or about 40 years of non-stop writing due to write cycle limits
Encryption	HDD's can overwrite encrypted data right on top of the old data	SSD's need a secure erase feature or total partition encryption. (Can not overwrite data, data must be erased first)
Cost	HDD's cost about $0.11 USD per gigabyte as of 3/17/2011	Solid state drives cost about $1.80 USD per gigabyte as of 3/17/2011
Sound	HDD's typically make noticable sound during read/write and spin up times.	Solid state drives have no moving parts and make no sound.
Heat	Very little heat produced, but still 3 times more heat than SSD's.	Only produce about 1/3 the amount of heat of an HDD.
Sensitivity to Shock	Very sensitive, hard disk drive heads and disks may break due to shock or vibration	Solid state drives have no moving parts and are very resistant to shock and vibration
Fragmentation	Level of fragmentation of an HDD will significantly reduce read/write speeds	No need to defragment solid state drives due to not having any read/write heads to find the data
Appearance
High Performance Example	Western Digital Caviar Black 640GB 3.5" SATA 3.0Gb/s Internal Hard Drive -Bare Drive	OCZ Vertex 2 OCZSSD2-2VTXE120G 2.5" MLC Internal Solid State Drive (SSD)

Last Updated on Saturday, 14 May 2011 15:51

Comments

0 #14 lyth0s 2011-08-14 16:56

@Johnny
SSD stands for solid state drive while HDD stands for hard disk drive. These refer to the amount of space on your computer, not how much memory they have. 160GB of SSD is the same amount of space as 160GB of HDD, but the SSD will run faster (will load files faster etc).

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+1 #13 johnny 2011-08-12 09:22

is 160gb of ssd memory the same as 160gb of hdd memory?

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+1 #12 Scott 2011-08-11 14:45

For many small writes SSDs can actually be slower than traditional hard drives are. There are many sites comparing real performance data of ssds vs hard drives and the hard drives beat out the SSDs in some cases where lots of small writes are concerned. Your web browser cache does lots of small writes, by the way (or when copying a bunch of small files).

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0 #11 Pollo 2011-08-10 05:28

What about their weights (in laptops for example)?

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0 #10 Paull66 2011-08-02 23:45

Just found this web site - excellent - answered all my questions on SSD and what to install (ie windoews, games etc)as plan to build my first pc (after buying them for 16 years). Thanks again for simple info for a novice pc builder.

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+1 #9 Lyth0s 2011-06-06 18:11

@jhayrom sierra
1GB of data on an SSD or HDD is exactly the same in terms of space. The only difference is that the 1GB on an SSD will load MUCH faster than it would load on an HDD.

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+1 #8 jhayrom sierra 2011-06-05 10:58

Guys. a little help. does anybody know what is the equivalent of 1 GB of SSD to HDD?

thanks,

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+1 #7 Lyth0s 2011-05-14 15:51

@Bryan
I added just general guidelines to heat and sound production of the hard disk drives vs solid state drives. Both HDD's and SSD's produce very little heat so hopefully that won't play a factor into which drive you use. The HDD's can be quite loud, especially ones that run over 10k RPM's. SSD's have no moving parts and make no sound during reading or writing data.

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-4 #6 bryan 2011-05-13 19:46

Im surprised they did not report on sound nor heat. How do these stack up?

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0 #5 Lyth0s 2011-04-24 13:33

@James Braselton
While what you said is not completely understandable to me, the hybrid SSD/HDD combos hard drives are interesting. They come with better speed than a normal HDD, but they are still pretty limited in the amount of space they have (around 250GB). If you are going to be limited to a hard drive of 250GB I would just spend the extra $40-$60 and get an SSD (if you want the speed) or keep the price the same and get a bigger HDD hard drive for the same price as an SSD/HDD combo.

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