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I've got a server with 16 1TB SATA drives in it. It was set as a single RAID5 volume. Unfortunately, Windows was showing two unallocated volumes during the windows setup, one as 2TB, and then the rest. I've been unable to figure out how I can utilize these volumes in the correct manner. The vision was to have two partitions:

100GB - OS Rest - Backup 2 Disk Partition

After calling HP, they wanted me to RAID1 two disks for the OS and then use the remaining disks in a RAID5 config. Once in Windows convert the RAID5 volume to GTP. However, this completely wastes a lot of space on the OS volume.

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What is the question? – mailq Dec 29 '11 at 23:11
How can I get it to work the way I wanted it to if it is possible? – Untalented Dec 30 '11 at 0:27
Use the RAID controller to built the RAID and a partitioning software before installing Windows. Done. – mailq Dec 30 '11 at 0:29
Is there a free solution that will allow me to do this? The partitioning portion. – Untalented Dec 30 '11 at 0:57
Yes, sure. Plenty. – mailq Dec 30 '11 at 1:03

I agree with HP - create a small RAID (2Tb or less) for your O/S - RAID1 with 2 drives sounds like a sensible option as you won't need blistering speed but redundnacy is nice. If you had an EFI BIOS you could boot from a GPT volume but I'm guessing if you did, HP would have told you to do so.

The problem you have is that traditional MBR volumes are limited to 2Tb max - anything else will be wasted. Once you have set up Windows, then set the 2nd RAID up as a GPT partition which will allow you to use the whole of the space.

Wiki on GPT partitions -

This discussion gives reasoning for MBR and GPT not being able to co-exist on the same partitions

This (very long) discussion seems to imply it can be done with certain tools, but makes no mention of exactly how, or any windows tools. I honestly reckon even if it is possible, the time taken would cost less than the storage you are trying to save!

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Certainly you want to be using GPT throughout wherever possible, there's little reason to use MBR these days, that'll help deal with the >2TB issue but you have a much bigger problem. That is that you REALLY don't want to have a 16 drive RAID5 array at all, you don't mention which controller you have or whether you're using it to create the array or Windows but a R5 array that size is a recipe for disaster. Very seriously consider migrating to RAID6 as soon as possible, yes you'll lose a disk's worth of space but that 16 disk R5 is going to die completely on you sooner rather than later. You may need to buy the HP SAA licence required to switch on R6 on your controller but it'll be money well spent. Oh and if you're not already I'd use the controller to manage the array rather than Windows.

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