RAID 0 is a process where, essentially, half of your data is written to one hard drive, and half is written to the other. So, for example, for a 2MB file, 1MB would be written to hard drive #1 and 1MB would be written to hard drive #2. Obviously, this has its advantages. If each hard drive can write 1MB in one second (numbers chosen for simplicity), it would normally take two seconds for a single hard drive to write a 2MB file. However, with each hard drive writing 1MB simultaneously, it should only take 1 second for the 2MB file to be written. The same applies when reading a file. If the a single hard drive could read a 2MB file in two seconds, then two hard drives could read 1MB each simultaneously in one second. So, theoretically at least, RAID 0 should give you a 100% performance increase.
In reality though, it doesn't. First of all, there is overhead for the RAID controller to process how the data will be split up between the hard drives. Also, there is the "stripe size", which determines how big each piece of each file on each hard drive is. If the stripe size is too big (say, 512kb), then all files smaller than 512kb (many system files which are frequently accessed are smaller than 512kb) will not receive any benefit from RAID 0, as they will all be stored on one hard drive. If the stripe size is too small (say, 4kb), then the RAID controller has to do extra work because the files are getting split into more parts. (A 1MB file would be split into just two 512kb stripes, but it would be split into 256 4kb stripes!) A common middle value, such as 64kb or 128kb, reduces each of these effects from the extremes, but still suffers from both problems. Also, the stripe size also suffers from "bloat". If your stripe size is 128kb, but you only have a 1kb file, it will still take up 128kb on your hard drive. So, you effectively have less room on two 320GB hard drives in RAID 0 than on one 640GB hard drive.
Also, don't forget that since your data is split between the two hard drives, if one hard drive fails you will lose all of your data. So, your chance of losing data is doubled compared to if you weren't using RAID 0.
Overall, the average performance gain from RAID 0 is less than 10%. If you have a really good RAID controller (found on dedicated RAID cards and meant for enterprise environments), you might get 20%-30%.
The 640GB Caviar Black I recommended easily has more than 10% better performance than the 320GB Caviar SE16, so it is really the better choice than two 320GB Caviar SE16s in RAID 0.
EDIT: For monitors, you're right, 22" monitors don't typically come with 1920x1200 resolution. I was thinking of 24" for some reason. Still, I think 1680x1050 is too few pixels for 22". This
is a nice 21.5" monitor with 1920x1080. If you are into HD, that resolution is 1080p, which is great if you want to hook up a Blu-Ray player to it.
Edited by stettybet0, 04 May 2009 - 08:43 PM.