HDD's (Hard Disk Drives) have been with us in various forms since their introduction by IBM in 1956. They have been in common use since the early days of personal computing, increasing in speed and capacity at an awesome rate.
However, there's a new kid on the block - the SSD or Solid State Hard Drive. This is compatible in every respect with a HDD, but instead of relying on magnetic storage like the HDD, or optical storage like CD's or DVD's, these types of computer storage devices use solid state electronic chips to hold the data.
SSD drives have a number of advantages over HDD's.
The faster speed is a significant factor in the popularity growth of the solid state hard drive. The access time is the same irrespective of the data's location on the SSD. Contrast this with a HDD where the access time is dependant upon the physical location of the data on the disk platter. Write access, whilst still respectable, is not curently as fast as read access.
Of course, on the see-saw of life, for every up, there is a down. The big down in this case is the price. The good news here is that the price is heading south at a respectable speed. It's the same phenomenon we see with most products - an introduction to the market at a high price, falling to a much lower, more affordable price as the market becomes more mature. Remember the way the prices of flash memory plummeted some years ago? I remember buying a 512kB SD card for my digital camera at a cost of over £50. A few years later, I could get one with 4x as much capacity for not much over 10% of the price!
So too with SDD's. The first drives were horrendously expensive for a very modest storage capacity. For capacities matching the larger hard drives, you were talking telephone numbers. As the price levels have fallen, the lower capacity SSD's can be considered as a straight hard drive replacement. These have reached a price level where they may actually be cheaper than the smallest HDD's now being produced.
A lot has been written about the limited lifespan of SSD's. However, even HDD's, being mechanical devices and subject to wear and tear, have a limited life span. The flash chips used in SSD's are capable of at least 300,000 write cycles, with best of breed capable of up to 1,000,000 write cycles. However, the manufacturers have come up with some clever algorithms to ensure the SSD's spread the write cycles uniformly over the whole disk. Once a block has been written to a certain number of times, the data in that block will be swapped with the data in another block which is read-only. This gives better disk life and in normal usage will give several years of trouble free use.
The larger SSD's are still much more expensive than HDD's of an equivalent capacity, although the difference is gradually being eroded. However, for the size of drive you would typically find in a carputer, the premium is not too high and in my opinion is worth the additional outlay to get greater reliability in the more aggressive environment in which it has to operate.
The other plus point about SSD's in a carputer is that most of the information flow is one way. Typically, you will have many more read cycles than write cycles and this will help disk longevity.
SSD or HDD?
Read more about HDD's