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Question

RAID

Aug 19, 2011 8:44AM PDT

<span id="INSERTION_MARKER">I tried
to convert two 80 Gig external hard drives into a 160 Gig hard drive using Disk
Utility's RAID function. <span>

<div><span>Surprise, I can only store 73 Gig on the RAID. That's
of no value.??</div><span>

<div><span>Either I have done something wrong (Don't understand the RAID
function) or I have to split the RAID back into two 80 Gig hard drives again.</div><span>

<div><span>??I
tried to restore the two drives and gave up after letting my Mac Mini run for
over 24 hours.??

<span>

<div><span> Help



</div></div>

Discussion is locked

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Answer
There are different types of RAID
Aug 19, 2011 10:43AM PDT

There are different types of RAID, or configurations if you like, and what it sounds like you did was set up disk mirroring. So there's an identical copy of data on both drives. What you wanted is called RAID 0 (technically it's not RAID, since the R stands for Redundant) or disk spanning. That probably would require reinstalling the OS, so you probably didn't see it as an option if one of the drives is a boot drive.

Generally speaking RAID 0 is a bad idea. One drive goes down, the data on both is inaccessible. There is absolutely no fault tolerance (which is the whole point of RAID) in that config.

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RAID
Aug 20, 2011 6:42AM PDT

Thanks for the response.

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Is it working?
Aug 20, 2011 6:49AM PDT

If so, then why not leave it as it is. If this is RAID 1 then you have a 'certain' amount of protection if one of the drives fails.

If it is not working anyway, then you have lost nothing.

I agree with Jimmy about RAID 0. It is not for the faint hearted. I've used it and I was always nervous that one of the drives would fail. If it had, then everything went without chance of recovery.

Mark

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If you want RAID 0
Aug 20, 2011 1:26PM PDT

If you want RAID 0, then yes, this would have to be done prior to installing the OS, because Disk Utility is going to wipe both drives clean in making the array.

Just be sure you have some sort of a backup in case one drive ever craps out, and remember that you won't be able to get back up and running until you replace that drive AND reinstall the OS to recreate the array. IMO, it's just not worth it when you can just separate what gets stored where. Like I have 2x2TB drives, and one is used for stuff I capture off my DVR and plan to delete after watching, and then I have another one where I store stuff I plan to keep longer term. It also has rips of my DVDs for streaming over my LAN. I briefly flirted with the idea of RAID 0, and just dumping everything into that, but then I thought about what would happen if one of the drives went bad. I'd lose everything as opposed to just one or the other. This way I may lose my archive or my current stuff, but it's highly unlikely I'd lose both at the same time.

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RAID
Aug 21, 2011 11:38PM PDT

Thabnks again for your input.

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No
Aug 22, 2011 10:44AM PDT

No. The closest you could come is having a disk image of the array, but if one drive failed, you'd still need to recreate the array before you could restore that disk image. There's no fault tolerance of any kind in RAID 0. One drive craps out, it MUST be replaced and everything reinstalled. Even using a disk image, you would have to recreate the array before laying it down or the results would be unpredictable, but probably unpleasant. You want any kind of fault tolerance, then RAID 1 is the best you can do on a Mini unless you buy some kind of external drive rack.

One other thing that came to mind, is Apple's software RAID controller can be a little buggy at times. One time at work, had a Mac Mini Server in with the 2x500GB drives set up as a 1TB RAID 0 array, and no matter what I did, the stupid thing refused to let me delete the array so I could restore the OS. Ultimately had to rip the thing apart, physically disconnect one of the drives from the MLB, then boot up the installer again so I could access Disk Utility, format the still connected drive, then essentially rinse and repeat with the other drive now that the array had been forcefully broken. It may be a rare occurrence, but it's REALLY annoying when it does happen.