Primer -
The drives you see in laptops aren't really designed with performance in mind. Sure, they'll do a lot better than a regular 5200 RPM disk, but they aren't designed to be drastically better than spinning disks in general. The focus is, as it always as in laptops, more on data integrity and power requirements, and the latest laptops with SSDs will do consistent read/writes that are about on par with sequential read/writes on a 10k RPM spinning disk, but obviously with a higher I/O capacity.
For desktops, the performance is obviously key, but the technology employed in off the shelf SSDs today is pretty much identical to what's in laptops. There are new drives coming with practically unfathomable performance, reaching 800MiB/s reads and 600MiB/s writes and I/O operations in the millions per second, but these are at least a year from hitting the general market, and probably three or four years from price tags where you would even begin to speculate about putting one in your machine.
So, what we have today is pretty much the first generation of end-user SSDs, and while read and write speeds are similar to high end spinning disks, what's amasing is the actual real-world performance you get.
Spinning disks spin. Which pretty much sucks. Spinning introduces seek time, mechanical latency and data volatility. When you make a request for data, not only does your harddrive have to handle the request, but it has to move the read/write heads to the position where your operation is to take place. If you have a fresh, clean harddisk, that's not -terribly- bad, as writes will be sequential - that is, they'll be written down at the same speed at which the platter spins, with no breaks in the process, and reads will be able to read bigger files "fluently" as a consequence of this. The problem is, though, that even the smallest bit of file fragmentation on the disk results in the read/write heads having to jump back and forth between many different spots on the disk to carry out the operations, resulting in a huge overhead of mechanical latency, to the point where your sequential 50MiB/s read and sequential 30MiB/s write disk will be lucky to pull 10MiB/s / 8MiB/s.
One of the advantage SSDs have here is that there's practically no access latency. Most spinning disks operate with access latency of between 6 and 10 milliseconds, while high quality SSDs measure access times in microseconds. Arguably the biggest advantage, though is that SSDs are flash memory. That means that when you're reading or writing files, you're reading and writing to logical positions on a static medium, and the disk doesn't have to wait to perform its operation, because the positions are instantly available. This means that operations that require reading or writing a ton of small files, or from different positions inside bigger files, such as gaming or loading complex applications, gain tremendously from the use of SSDs, and this consistency across operations, circumvention of disk fragmentation, and involatility is what makes SSDs extremely appealing for very many computing tasks.
Benchmarks -
Sadly I haven't been able to find any benchmarks on any of Micron's SSDs, but I did manage to find a benchmark test comparing SuperTalent and Samsung's SSDs to a regular spinning Western Digital disk. These are upper range. ~$800 SSDs, though, so how the scores translate to mid and lower range drives, I do not know.
Access timeReal-world performance
Last edited by mikkel (2007-11-30 06:26:08)
