RAID 0 setup on MAC OS X v10.4

First, it would not have hurt to know your actual machine. You should know that the type of Raid 0 that you are talking about achieving  is software raid not hardware. This means that the speed of the array is very much cpu dependent. If you are talking about a G5 or newer then you might get small gains . Yes, when you set up a raid array you are talking about a complete reintialization of both drives so that a virtual striped drive can be setup.  There is no way around this. Mac os X does make it easy to clone your current driver image, however, as a bootable option but you will need a place to store it while you are setting up your raid array. Something like an external fireware drive or a drive on a MAC  friend's network or puter. Because raid 0 has no redundancy(HEHE is it really RAID?) you will end up with one 500 gb logical drive. That being said, you also need to know that if one of your drives ever fails then your entire boot image will be irrecoverably lost because of that same lack of redundacy. In general, it is not a good idea to have a boot drive be setup in raid 0 for this reason( Unless you are just gameing with it).  If you want a good source of articles about the pros and cons of a raid 0 boot drive go to www.barefeats.com and look though past articles. I think you will find several.

Thanks for your reply. I am actually running a G5 PowerMAC Quad Core 2.something processor (sorry can't remember the exact processor speed), but it was the type released just before the new Intel Chips arrived. The reason I was interested in running RAID 0, is a few of the computers here at work (XP computers) have RAID 0 setup, and they run really quick. And since I am running low on space on my 250GB drive, and was thinking of getting a second HDD, I thought it would be a good idea to set up RAID 0 myself. I will have a look through the link you sent. Cheers.

pheidius... you said Mac OS X makes it easy to clone the current drive image... how would I go about doing this.. I have a Lacie External 320GB firewire/usb 2.0 HDD. And in reference to what you said about if 1 HDD fails then the entire bootable image will be irrecoverably lost.. wouldn't this be the same for my bootable drive even without the RAID?

Expert Advice !!

RAID 0 is very, very dangerous to your data.  

Not only is there no protection for your data, but the use of RAID 0 at lest doubles your chance of data lost.

If either drive has a failure, then the data on both drive is corrupted and usually not recoverable...

Anyone running RAID 0 in a business situation should be blacklisted and no longer allowed to work as a systems administrator.

Now to answer your question, you cannot create a RAID volume (except RAID 1 in some unix versions) without having to completely reload your data.  So, as pheidius said, you will need to back up your existing data, and store it somewhere else while creating the RAID.

Ok, the truth is here that your reasoning here is a bit suspect and your need for raid O minimal given the risks. As I said, Barefeats did extensive testing looking for the ideal boot drive for your quad 2.5. The following will give you an idea of the flavor of the article, "Based on the mixed gains of the RAID pairs over single drives, I hypothesized that there are more advantages to having two independent drives as opposed to a bootable RAID 0 pair. Why? Because things don't happen in sequence. Your normal work flow causes storage events to happen in parallel. To simulate this, I started a duplication of a large file then launched Unreal Tournament 2004. The graph below shows how long it took for UT2004 to finish launching in three configurations: same drive, separate drives, and RAID pair:..." and so on and so on. http://www.barefeats.com/hard63.html  If you read the article all the way through, the final and far more secure recommendation is to use two indidual drives, one for boot and one for user and data files. That being said I can tell you that I also have a quad 2.5 and run Raid 0 with it and I get screaming consistent bandwidth throughput of over 200 mb(230-240 ish). But I use hardware Raid 0 as I imagine your cited Pc's do at work. Now my setup is a bit more expensive as I use a RocketRaid 2320 in my 4 times slot. This is hooked to 4 10,000 rpm Raptors. Now this is not a bootable setup but, even if I could, I would not boot from it. I use it as a high speed video rendering scratch disk. This, however, is what RAID 0 is designed for "high throughput temporary storage space." That is why I poked fun at even calling Raid 0 RAID at all. The R in RAID stands for redundant but raid O has no redundancy only high risk speed and full use of the additive sizes of all drives.
To answer your question, though, you can use disk utility to create a bootable clone. Or if you want an easier time of it, you can use Carbon Copy Cloner v3 beta to achieve the same result. There are probably for or five other utilities out there that will do the same but CCC is nice cuz its free.
http://www.bombich.com/software/ccc.html
I would still recommend not doing this as part of a boot scheme.  If you want and need RAID 0 then pay the extra money for hardware raid. Besides, you may just be experiencing sluggish drive reads and writes because in filling up your boot drive you are now always working on the slowest part of your drive. Many experts recommend using a "short stroking" scheme wherein you buy a larger slower rpm sata drive and then partitioning it so that you lose some of its total space but thus always keep the fastest part of the drive in play over paying the bigger dollars for an expensive 150 gb raptor boot drive.
So if you want more detailed advice in how to do it let me know but I would suggest that there are better options.

ok so to set up hardware raid what steps would I need to take to do that and what hardware/software would I need? I take it that you also recommened that I keep the existing bootable drive separate, and have minimum of 2 new drives hooked up to a RAID card? or maybe just buy a smaller drive to use as the bootable one which will hold the OS, and buy another 250GB to use in the RAID 0?  sorry if these are silly questions, I am only new to mac, and the only RAID experience I have is on IBM servers at work using RAID 1 and 5.

Thanks for the info. it has definitely helped.