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I have two internal hard drives: a 4TB drive and a 750GB drive. After selecting RAID0 and installing Debian (wheezy) to a single partition, I ran fdisk -l which reported that the size of my root partition (/dev/sda1) was 1.4T. So, I've got a couple of questions....

1) I know that fdisk only allows up to 2TB so even if my (4TB + 750GB) drive was being restricted to 2TB, what happened to the other 0.6TB? Remember, I installed everything to one partition.

2) My ultimate goal is to have everything on a single 4TB partition. I've read about parted but everything I read relates to partitioning and mounting a non-bootable partition. This doesn't apply to me as I'm using a single partition which contains /boot. What are my options?

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  • Could you clarify your question. 1. How are you using a raid 0 with two different sized drives? 2. Is your drive GPT or MBR,
    – spuder
    Commented Jul 29, 2013 at 6:57
  • What is your kernel version ? With v0.90 raid superblock and kernel <3.1, you have severe limitations. see : raid.wiki.kernel.org/index.php/RAID_superblock_formats
    – mveroone
    Commented Jul 29, 2013 at 7:55
  • @Kwaio: Kernel is 3.2.0-4-686-pae.
    – Ash
    Commented Jul 29, 2013 at 8:00
  • Is your OS 64bit ? Is it up to date ? specifically, HBA drivers...
    – mveroone
    Commented Jul 29, 2013 at 8:02
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    @spuder: I see. Well the SAS configuration utility on my Dell server gave me two options to set up the RAID array: mirroring and striping. I chose striping. I thought that would have given me maximum space but I guess I was wrong. You're correct. I've ended up with 2 * 750GB = 1.5TB worth of space.
    – Ash
    Commented Jul 29, 2013 at 8:14

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Just to sum up what we came with in the comments, here is your problem :

You are doing stripping (alias RAID-0) over two drives :

  • a 4 TB one
  • a 750 GB one

The size used on every drive of a RAID0 array is equal to the size of its smallest drive. Thus your array wil be 2*750 GB = 1.5GB. Removing a bit of overhead and GiB/GB confusion, this came up with a 1.4TB array.

From there your only option is to use your drives separatly (which you seem to be unable to do using your SAS card) or replace the small drive by a 4TB one.

Anyway, remember Stripping is unsafe as any drive failure will result in the loss of data stored on both disks, because any block of data is split between both drives.

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    One more comment: Once these problems are dealt with, GPT is more-or-less required to make use of an over-2TiB disk. Thus, the MBR partitioning should be scrapped and parted or gdisk (not fdisk, except very recent versions) should be used to set the disk up with GPT. Also, I do not generally recommend using a single partition on such a big disk. At the very least, root (/) should be separated from user data (usually in /home for workstations; often in /var on servers), and a separate swap partition is often in order.
    – Rod Smith
    Commented Jul 29, 2013 at 14:18
  • For some reason, swap turned out to be in a separate partition by default. The server is primarily used to backup another server and it is itself backed up on a regular basis. So there's no need for home directories and I am not worried about data loss. Thanks a lot for all the responses.
    – Ash
    Commented Jul 30, 2013 at 2:37

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