Almost every computer purchased in today's world contains an hard disk drive (HDD), with some of the more specialized computers more recently coming with solid state drives (SSD). HDD's work in a similar way as a CD or DVD. The disks, called platters, rests on a spindle that spins up the disk when information is needed, while a few optical lenses read the information from the disk. Most hard drives spin at about 7,200rpm, that's fast right? No. While it may seem like quite a bit of speed, with HDD's you only get around 50MB/s of speed, while some of the latest SSD's get speeds over 200MB/s.

SSD's contain no physically moving parts, thus the electricity within them basically movies at the speed of light. There are some issues with SSD's however. Most are woried about how long the drive lasts. Most new SSD's have a MTBF (mean time between failures) of 1 to 2.5 million hours, meaning that eventually, with the limitations of NAND memory, the SSD will fail. There is no hard evidence yet that an SSD cannot hold information for long periods of time (20 years or so), but they are not expected to.

Many manufacturers have been using SSD's for several specialized reasons. Netbook vendors have been using SSD's because of their speed, light weight, and size; measuring at 2.5 inches, they are desirable for netbooks. Most desktop hard disk drives weigh considerably more than an SSD, and are physically larger, 3.5 inches to be exact. What SSD's lack in storage space, they make up for in speed, being 2,4, even 6 times faster than an HDD.

The platters of a hard disk drive can hold information for possibly one hundred years. However the actual drive itself, spindles, arm, etc... only have MTBF's of 600,000 to 1.5 million hours. Compared to 2.5 million hours with an SSD that doesn't look too promising. 

Netbook vendors such as HP, Acer, and Dell are reporting that they may abandon the use of SSD's in netbooks. Why? Apparently because they are afraid that the SSD's will not retain information for an extended amount of time. Many manufacturers have "patched" this issue by integrating firmware that moves the data around on the disk.

While an SSD could last much, much longer than an HDD, the memory it contains cannot. I can't say that I'll just leave my super-fast SSD just sitting there and never use it though.

Source: Cnet