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Will MBR work with a 6TB array for data

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April 13, 2011 5:33:29 AM

Alright, I just want a straight up yes/no answer to this. I have a 6TB array (running off an hardware raid card). I am running Windows 7 64 bit. Should I format it as MBR or GPT? If I format it as MBR, will I be able to:
1. Make partitions larger than 2TB (for ex, a single 6TB partition)?
2. Make partitions past the 2TB 'boundary' (for ex, if I can't make a 6TB partition, can I make three 2TB partitions)?

Becuase if not... I'm going to have to find some way to convert the existing 1.5TB array to gpt before OCE-ing it...
a c 415 G Storage
April 13, 2011 5:55:37 AM

If you use an MBR partition table you won't be able to use any more than 2TB of the volume, and so obviously you won't be able to create any partitions larger than 2TB.

On volumes larger than 2TB, GPT is the only effective partitioning scheme available.
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a c 289 G Storage
April 13, 2011 2:47:48 PM

What I think (but have not tested)

If you create it as MBR, everthing past 2 TB is useless.

The GPT is supported for all purposes except booting in Server 2003 SP1, Vista, Server 2008, and 7. If you are running one of these OS versions, you can format a 6 TB (or TiB) partition using GPT and the OS will be able to read and write data.

Booting is another issue. Only certain EFI motherboards can boot from a GPT partition, so you are unlikely to be able to use the RAID as a boot (did you want to?).

From Microsoft: http://msdn.microsoft.com/en-us/windows/hardware/gg4635...

A final clarification: GPT and MBR are disk-level schemes, not partition-level. So breaking a big drive into 2 GB partitions will not solve the problem.

Edit: The intro on this page seems more useful / concise: http://msdn.microsoft.com/en-us/windows/hardware/gg4635...
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April 13, 2011 4:24:13 PM

Alright, cool. Nowhere I searched before explicitly said "You can't use more than 2TB of your drive/array if you use MBR" which is what I was looking for. Thanks guys.
Le sigh... maybe I should just keep my existing array and make a 4.5 on top of it....
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a c 415 G Storage
April 13, 2011 6:45:26 PM

Many RAID controllers will allow you to create several 2TB volumes from a large array. For example if you have four 2TB drives configured as a large RAID-5 array with 6GB of available storage, some controllers will let you divide the 6GB up into three 2TB logical volumes that are visible to the OS. You'd be able to use MBR partitions on each of the 2TB logical volumes even though they are coming from a 6GB storage pool, because the RAID controller is handling the 6TB pool and not the OS.
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April 13, 2011 11:12:10 PM

Yeah, I know. Problem is my controller (Rocketraid 2310) doesn's support more than 4 arrays per drive. So what happens is if you hit that limit, you can no longer OCE/ORLM because when you migrate or expand, it needs a 5th array as the destination array. I could have 3 arrays but that's cutting it kind of close to 4, so I just want to keep it simple and have as few arrays as possible. I'm going to keep my current 1.5TB MBR for 'compatability' and make another array with GPT for the rest of the space.
Btw, does GPT like having arrays magically growing larger and larger under it? MBR didn't care as far as I could tell, but I read somewhere GPT puts information all around the volume...
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a c 415 G Storage
April 14, 2011 1:10:51 AM

> Btw, does GPT like having arrays magically growing larger and larger under it?

GPT puts a redundant copy of the table at the end of the volume, so if the volume expands underneath it then the redundant table will be mis-located. But that's nothing that couldn't be corrected with smart enough partitioning software.

Unfortunately I'm not a partitioning expert and I can't tell you if or what software could handle that situation.
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April 14, 2011 11:49:51 AM

Well, I just tried making a 1GB test array, initialized it using GPT, put some stuff on there. Then resized it to 2GB. Window's disk management utility didn't even miss a beat; showed the extra GB on the end and I resized the existing partition quite easily. Soooo.... I guess windows 7 is just smart? Can someone verify if they had problems doing this with previous versions of windows and don't anymore with Win7?
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April 21, 2011 12:34:49 AM

Best answer selected by billyboy999.
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