JFreak said:
do you have any idea what you're talking about?
yes, raid0 makes things a bit faster, but it also has zero error-tolerance, which means should either drive fail you lose everything. raid0 cannot be reconstructed and having one without backup is even more risky than having a single hard drive that you kick every now and then.
raid1 on the other hand is slower than single drive. while it offers error tolerance, it will take double the time to write anything to the raid array of two drives, and the read performance of a software raid is not optimized either. so you get a backup but will also take a performance hit.
you would have to have a very huge raid array to make many 3600rpm (?) or even 4200rpm drives achieve the speed of a single 7200rpm drive. have you ever wondered why the REAL raid arrays of the server cabinet run 10000rpm or 15000rpm speeds? raid is not used to get more speed. it is used to get more fault tolerance. (yes, it can be optimized for speed, too, but that requires a hardware raid controller.)
I'm glad somebody replied to my post.
I freely admit, I have no first hand experience with any kind of RAID array. But I'm not really sure who is the one of the two of us who does not know what he is talking about.
RAID arrays can, as far as I know, be used for three purposes (and combinations thereof):
- live mirroring (ensuring data integrity when a physical drives fails)
- creating a bigger 'virtual' drive (if you have a lot of data)
- creating a faster drive (e.g. for capturing video at high resolution, or streaming of data)
The first purpose (or combinations including it) is probably what most RAID arrays are used for.
But the last option, a striped array (the second option is also a striped array, to be precise), also is used a lot.
I admit that the risk of data loss essentially doubles (due to a harddrive failure) when you use two drives for a striped array but that does not have to be a show-stopper. What I don't know is whether OS X can boot from a soft RAID if not this could be a deal-breaker since a hardware RAID might be too expensive still.
Here is one example of not-so-serious striped array which clearly shows how this can speed up transfer speeds:
http://ohlssonvox.8k.com/fdd_raid.htma
And naturally, if your main aim is speed, as in a server, you start with the fastest drives available and then build a RAID with them (10 000 to 15 000 rpm drives), but in a Powerbook you have to balance speed against size and power consumption.