what does the cache mean on a hard drive?

[lil sleepy]

i see on some hard drive 16mb and some are 8mb. whats the difference? the more cache the faster it is?

[Snugglebear]

That's the hope. In reality the performance boost isn't all that great, but since the price difference isn't very large, I wouldn't worry about it. Cache is used to store data prior to be written to disk as well as store data that's just been read off the disk. In the former case the cache buffers the write and allows the drive to flush the data to disk when it is convienient, rather than tie up further operations dependant upon it. In the latter case, most drives read some arbitrary amount past the requested addresses in the hope that later read requests will be in that area (locality of reference is very common, moreso in single user/desktop environments). Both of those increase the apparent speed of the drive, but understand cache is also used to store working microcode and data for the onboard controller.