raid setup problem

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raid setup problem

MacPro 2010 - OSX 10.9.5

I meant to set up a Striped RAID using two of the drives in my MacPro. I Installed two 5TB drives and set them up as a RAID, but inadvertently chose mirror rather than stripe. So I thought easy - I will just erase the drives and start again. But now I end up with two 5TB drives showing up and I cannot go back and make them into a RAID - the option just does not appear. I have two other drives in the tower that are also set up as a stripe - so I have some (limited) idea of what I am doing.

Please, any suggestions. The drives are of course empty of data. Thank you

Mac Pro, OS X Mavericks (10.9.5)

Posted on Jun 26, 2015 10:51 AM

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Answer 1

Jun 26, 2015 11:11 AM in response to JimP101

A bug in Disk Utility ERASE function from 10.8.4 onward leaves Internal drives (over 2.2TB) set up as a Core Storage Group, and the rest of Disk Utility cannot do anything with that.

Solutions include:

• Use an older version of Mac OS X including to 10.6 DVD (if your Mac Pro can boot from it) to ERASE again.

• Use an external enclosure to erase again.

• Use some fairly obtuse Terminal commands to delete the Core Storage Data Structures, leaving a "regular" drive which can then be manipulated. If you need these, ask and readers can find the links to earlier posts that contains instructions.

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Answer 2

JimP101 Author

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Jun 26, 2015 11:14 AM in response to Grant Bennet-Alder

Wow - that all sounds quite complicated for a simple mistake...!

I do have Newertech Voyager dock for a bare drive so I guess I could use that and erase each in turn.

Thank you

Jim

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Answer 3

JimP101 Author

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Jun 27, 2015 1:08 AM in response to JimP101

An Update - following on from the advice given above I connected the drives in turn to another Mac (Mac Mini) via an external dock and erased them there. I was then able to return them to the internal bays on my MacPro and set them up as a new 10TB striped RAID - which will now become my Time Machine. I believe this is what techies call a 'work-around'........

Problem solved.

Thank you

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Answer 4

Jun 27, 2015 6:54 AM in response to JimP101

Striped RAID's claim to fame is that it is faster than JBOD (Just a Bunch of Drives) which is the other way to get your two drives combined into one BIG Volume. JBOD (also called Concatenated Disk Set) is also available directly in Disk Utility.

Striped RAID's tragic flaw is that if one drive drops out due to an error, the RAID is broken, and with alternate "stripes" on Alternate drives, the entire Volume is usually lost when this happens, and NO files are recoverable. Users who need a big fast drive for editing large Video files are willing to treat the striped RAID as a temporary holding place, and keep copies of their permanent work elsewhere.

If this were mine, I would use JBOD to concatenate the drives for a Big Backup Volume. In case of a total drive failure, you could probably get some of your files back from the undamaged drive. In case of a minor failure, only a few files would be totally lost, and others may be salvageable.

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Answer 5

JimP101 Author

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Jun 27, 2015 7:18 AM in response to Grant Bennet-Alder

Grant, thank you for taking the time to reply. Your point is well made and before using my new Stripe RAID I will have a think...

For what it's worth my set up is -

OWC Mercury Accelsior 480GB SSD with Applications and Adobe Lightroom catalogues. About 250 GB in use.

Two 4TB WD Black drives in an 8TB RAID stripe with all current pictures and video - currently around 4TB stored.

Two 5TB WD Red drives in a 10TB RAID Stripe (the one in question) which is currently empty but destined to be my Time Machine backup.

An external e-sata OWC device with Four 4TB WD Red drives installed as RAID 5 - giving 12TB of storage. My plan is to regularly clone the contents of the 8TB RAID to this external drive.

So my strategy is that the main 8TB raid and SSD are hourly backed up to the 10TB raid by Time machine, and then I additionally clone the 8TB raid to an external raid-5 backup.

I appreciate nothing is really foolproof, but I would be unlucky to loose both Raids at the same time and even then I have my cloned backup. Or have I missed something......haha!

Incidentally I am a photographer by trade so my data is fairly important.

Jim

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