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I'm using a Supermicro X9SRE-3F motherboard with the latest BIOS and 2x 4TB drives connected to the on-board SATA controller.

If I set the BIOS to RAID and create a RAID 1 array, the array shows up in the BIOS as 3.6TB. However when I boot Windows (on a separate RAID 1 array), the 4TB drives show up individually in disk manager as 2x 1.62TB drives.

I could use Windows 2012 to set up software RAID 1, but when I set the BIOS back to 2x individual drives, they still show up in Windows as 2x 1.62TB drives.

How do I access the full capacity of these drives?

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2 Answers 2

If a drive is formatted with a MBR then the maximum recognised size is 2.2TiB.

Now this works slightly counter intuative when you use drives larger than 2.2TiB.

  • A 3TB drive on a system supporting up to 2.2TiB will show up as 3TB-2.2.TiB, which is about 750GB.
  • A 4TB (marketing TB, probably slightly less) minus 2.2TiB is about 1.6TiB.

You might be able to use the full drives if you partition then with a more modern scheme, such as GPT.

You will either need a motherboard which supports booting from a GPT partition, or you will need to boot from a different disk and let subsequent drivers figure things out.

All modern motherboard should support booting from a GPT partitioned disk, but it is new enough that there are still quite a few boards with problems. (I did a quick search in the manual of the X9SRE-3F but found no reference to GTP. )

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Assuming the hardware is capable of supporting UEFI, you may want to review the following document:

Installing Windows on UEFI Systems
http://download.microsoft.com/download/0/0/b/00bba048-35e6-4e5b-a3dc-36da83cbb0d1/UEFIGuide.docx

In particular:

"When you are installing Windows, you may need to explicitly instruct the computer to boot in UEFI mode.

"Some UEFI platforms support booting in BIOS mode, and it is not always apparent whether UEFI or BIOS is the default boot option. If you do not explicitly instruct the computer to boot in UEFI mode, Windows Setup might install Windows in BIOS mode. This would not give you the advantages of UEFI."

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