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Old Jul 27, 2007, 09:19 AM   #1
Sean Dempsey
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RAID 0 with partitions - partition drives before making raid?

I am planning on using 2 320gig drives for a RAID 0 setup, but I want the raid to be partitioned. Do I partition the drives with 2 exact partitions first, and then combine each partition into a raid, or do I make the raid first, and then partition the virtual disk?

And if I do partition first before making the raid, can I do that right from OSX, or should I do it from the boot DVD disk utility?
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Old Jul 27, 2007, 09:29 AM   #2
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if you want the full drive, RAID first, then partition.

i believe however, you can make a RAID array from partitions in OSX, so you could say, make a 20GB partition (at the beginning) and one more that fills the remainder on each disk, then RAID the two 20GB partitions for Über speedy raid

if its a secondary (ie, data) drive, you can do it booted from the installed OS, if its to install the OS onto, you will need to boot from the DVD to do it (which you have to do to install anyway)
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Old Jul 27, 2007, 09:49 AM   #3
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well this is interesting

I made the partitions first, 3 of the same size (as close as I could get in disk utility) in 50, 100, and whatever is remaining gigs. I was able to raid the first 2 partitions, but not the last, they were just disks

so I reformatted the drives as 1 partition each, raided them, but now I can't partition that raid.

Did I do something wrong the first time, where I couldn't raid the final partitions on each drive?
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Old Jul 27, 2007, 10:12 AM   #4
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Okay, retried partitioning the drives first (read that it doesn't always work exactly) and I was able to make 3 partitions each, and combine them into 3 striped raid volumes.

So now, I have the 3 volumes I wanted, each a striped pair of partitions.

Although, Disk Utility did crash on me when it was finished. I reopened it and it appears fine. Wasn't very confidence inducing, but something risky like a raid with partitions is risky I guess.

Anyone want to comment on this? Is this normal for something of this nature, to not be an exact science to set up?
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Old Jul 27, 2007, 01:06 PM   #5
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RAID is generally done on entire disks, not partitions... can't think out why you can't partition if afterwards :S
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Old Jul 27, 2007, 01:32 PM   #6
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Quote:
Originally Posted by pengu View Post
RAID is generally done on entire disks, not partitions... can't think out why you can't partition if afterwards :S
I don't know, but disk utility didn't have an option to partition a raid once it was created.

After pre-partitioning the drives the exact same, the second time I tried, it worked and now I have 3 volumes running off the same raid.

That's what I read in this article: http://macprojournal.com/partitions.html

maybe if there is a way to partition the raid after you create it, someone could shed some light on that.
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Old Jul 27, 2007, 05:11 PM   #7
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In case anyone was reading this thread, I was able to successfully partition 2 drives and create 3 virtual raid0 drives out of them.


So far, it's really fast. The benchmark numbers I have been using are a great deal higher than before, and the speed that my files and things load and read/write is increased too.

If you have a good backup solution, I think I would recommend at least 1 raid0 setup in a Mac Pro.
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