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I just configured 4 3TB drives in a RAID-10 configuration but the total disk space in the RAID is 4TB. I used the following guide to setup the RAID-10, RAID-10 Intall. Shouldn't the size if the RAID-10 array be 6TB? According to this RAID Calculator it should be. Anyone have any idea of what might have gone wrong in the install?

Thanks in advance for your time.

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Verify that these drives have a GPT on them and not an old MBR partition table as that would limit the drives to 2TB. – 3dinfluence Mar 1 '12 at 17:10
up vote 5 down vote accepted

It should be 6tb... IF the raid controller of any sort can deal with more than 2tb per "partition". If it can not, then it will only use TB of the 3TB per disc.

2TB is a limit for discs, so that could be it - depends how the disc is formatted (not the resulting partition) by the controller.

has a discussion about that, including some reasons for some controllers.

It is possible the controller imposes sucha 2tb limit per disc.

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I strongly agree with the 2Tb limitation. Lots of RAID cards need a firmware update to support more than 2Tb per drive. – Gregory MOUSSAT Mar 1 '12 at 17:04
This is Linux soft (md-)raid, not a controller. – adaptr Mar 1 '12 at 17:06
@adaptr - but the disk/s talk to the OS via a controller - clearly that controller can't deal with >2.25TB disks - this is a VERY common problem that will require you to get a new controller and rebuild your array from scratch, you may need to ensure you have a kernel that'll support that controller too. – Chopper3 Mar 1 '12 at 17:11
Intersting, so what it I partitioned the 3TB drives into a 2TB and a 1TB. Then created 2 RAID-10s one with the 2TB and the other with the 1TB partitions. Would something like that work? – thiesdiggity Mar 1 '12 at 17:27
No. If the controller can not see more than 2tb - you are dead. Yes, if the controller can see it jsut not sue more than 2tb in a volume. Guewss what - try it out. First check bios of all hardware for updates. – TomTom Mar 1 '12 at 17:39

What does fdisk -l report in terms of partitioning?

What is the output from cat /proc/mdstat ?

If you've mounted the md0 array, what does df -h report ?

FYI the total available array space of 4x 3TB in RAID-10 is 5588 GB

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Since fdisk doesn't support GPT yet I'd use parted -l when trying to print out the partition tables and disk information on large disks. fdisk will just print out how large the GPT is but has no visibility into the partitions it contains. – 3dinfluence Mar 1 '12 at 17:29
@adapter parted -l shows each 3TB drive as 3001GB and for the md2 (RAID-10) shows it as 4398GB. So I think that it is an issue with Ubuntu's software RAID controller. – thiesdiggity Mar 1 '12 at 17:37
@thiesdiggity Update your question with the full output of parted -l and cat /proc/mdstat for a start. Help us help you. We are flying blind here and people are guessing at what your problem may or may not be. Essentially wasting time. – 3dinfluence Mar 1 '12 at 17:58

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