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question about RAID

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I am thinking setting up my system with RAID (RAID 0 in particular) but I am not iffy about doing that after asking around people.

Here is what I found out:

 

1. With RAID setup, I need two hard drives which I have two. IBM 30gig and 45 gig.

 

2. RAID setup requires both HD to be the same size and I think both my HDs are fine except that I will lose that 15 gig from 45gig HD.

 

3. After I setup my HD with RAID, I will not get 60gig total but just 30 gig from both HDs.

 

So my question is is there anyone out there with RAID setup? Is it worth it to give up Gigabytes of HD space to run your system with RAID setup? Because if the performance I get with RAID setup isn't that great then I am just gotta setup my system with just regular setup with 2 HDs with total space of 75 GB.

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RAID 0 is striped, generally running the total of the lowest common denominator (smallest disk size) times the number of disks.

 

RAID 1 is mirroring (or duplexing if multiple controllers are used) and is equal to the lowest common denominator (smallest disk size).

 

RAID 5 is the striping of data with parity across all disks and is equal to the lowest common denominator (smallest disk size) times the numbers of disks, minus the reciprocal of the number of disks. For example, you have 5 20GB disks, and you want to run them in RAID 5. You would have 100GB total, less 1/5 (20% or 1 disk) which equals 80GB. You will lose roughly 1 disk worth of space to parity in this configuration.

 

I hope this answers your question as far as disk space, as you should have about 60GB rather than 30GB in a RAID 0. Think of "0" as "Zero Insurance".

 

------------------

Regards,

 

clutch

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Clutch, thanks for replying. I have Abit SA6R motherboard and it has RAID controller built in. I just ordered 45gig HD and I have 30gig HD in my computer right now. The manual didn't say anything about RAID 5 so I am assuming my RAID controller doesn't support that mode. From the manual it say that I can do RAID 0, RAID 1, and RAID 0+1. But RAID 0+1 requires 4 Hard Disks so I won't be doing that. So the only choice left is to go with RAID 0 setup which will give me 60 gig. Do you know if RAID 0 is faster than Ultra ATA/100 setup?

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Depends on the drives and the controller. I am not familiar with your other config options, but here's the deal. A hard disk states that it is ATA100 compliant. Now, it may burst at 100MB/s, but it will probably not hold that rate as an average. If you get 2 hard disks in RAID 0 (parrallel), then there is a much higher possibility of hitting the peak of the controller (which is cool, since you would like to utilize as much of the hardware as you can). If you have 2 ATA66 drives, and an ATA100 controller, the odds are slim that you will peak that very often since the theoretical peak would be 132MB/s and you may average about 50%-70% of the b/w of the drive spec. If I didn't answer your question (which is likely), it is because I am in class for this wonderful Winnt to Win2K exam until 10:30PM. I will review this at work tomorrow to see if it makes sense...

 

smile

 

------------------

Regards,

 

clutch

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Yeah that explains a lot of things. Like my current 30gig IBM Ultra-ATA/100 never reach 100mb/sec even though I also got Ultra-ATA/100 controller. Let me see if I got this right...so if you have Ultra-ATA/100 and if both HDs are also Ultra-ATA/100, if I do RAID then, I would get theoretical rate of 200 mb/sec? I am probably not gonna run RAID after all now. Even though performance w/ RAID setup looks very good, I don't feel like wasting 15 gigs of it on my new drive (45 gig). But I know more about RAID than I was yesterday. Thanks.

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