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I'm trying to create a raid 6 array on a VNX 5100 from EMC, however am unable to create one with 7 drives. We have 8 total, and I immediately carved one out for hot sparing, leaving me 7 data drives. I can create one with 6 or 8, not 7. I am also unable to make a raid with 5 drives, which leads me to believe that odd numbers of disks are not eligible for raid 6. Raid 5 gives me no such issues.

Raid 6 should not have a dependency on having an even number of drives. Its only dependency should be meeting the minimum number of 4 drives. Can anyone help me find a way around this?

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Small nitpick: The minimum for RAID6 is three drives, not four, at least in the general (non-EMC?) case. – SvenW Oct 24 '11 at 16:54
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Not really- the standard cites a minimum of 4. en.wikipedia.org/wiki/RAID#Standard_levels. Otherwise you'd just essentially have a 3 way mirror. – Basil Oct 24 '11 at 16:58
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This is probably not what you want to hear, but.. this really sounds like a question for EMC technical support. It also sounds like it would probably cost less money if you just bought another drive. – user606723 Oct 24 '11 at 17:09
@user606723 Assuming there's space for another disk in the shelf. – MDMarra Oct 24 '11 at 18:00
We're going to have to buy another drive- that's annoying, but at least we have room in the shelf :) – Basil Oct 24 '11 at 19:29
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Here's an EMC PDF. Page 6 is what you are looking for.

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EMC implements RAID6 using the EVENODD technique, which requires an even number of disks.

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.88.332

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Get me a link to an EMC document to that effect and you've got the check :) Thanks! – Basil Oct 24 '11 at 19:04
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