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So yesterday, I had Ubuntu 12.04 on a 1tb standalone drive, and a hardware RAID 1 array of two 1.5tb drives. The RAID is setup in the BIOS, and has functioned as expected on Windows and on Ubuntu 13.04.

Today, I installed Xubuntu 13.10 on the standalone drive. So NO changes made to the RAID 1 array.

Booted into Xubuntu, and now the RAID disks show up as two separate disks, (SDa and SDb,) and can both me mounted and modified. However, changes do not "sync" between the two disks.

So, with no changes made on the hardware RAID side, why did Ubuntu recognize my RAID array as 1 unit, and function properly with it, but Xubuntu does not?

Will I have to implement a software solution in order to resolve this? And if so, is there any way to implement that software solution without having to wipe the drives and start fresh? I don't exactly have 1.5tb of free space hanging around to back everything up to and start over.

Thanks. Results of fdisk -l below, and the top two drives are the two that are supposed to be in hardware RAID 1:


Disk /dev/sda: 1500.3 GB, 1500301910016 bytes
255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0b2dac61

 Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048  2929684479  1464841216    7  HPFS/NTFS/exFAT

 Disk /dev/sdb: 1500.3 GB, 1500301910016 bytes
 255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 sectors
 Units = sectors of 1 * 512 = 512 bytes
 Sector size (logical/physical): 512 bytes / 512 bytes
 I/O size (minimum/optimal): 512 bytes / 512 bytes
 Disk identifier: 0x0b2dac61

  Device Boot      Start         End      Blocks   Id  System
 /dev/sdb1            2048  2929684479  1464841216    7  HPFS/NTFS/exFAT

  Disk /dev/sdc: 640.1 GB, 640135028736 bytes
  255 heads, 63 sectors/track, 77825 cylinders, total 1250263728 sectors
   Units = sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  Disk identifier: 0x72ad4fdb

   Device Boot      Start         End      Blocks   Id  System
  /dev/sdc1   *        2048      206847      102400    7  HPFS/NTFS/exFAT
  /dev/sdc2          206848  1250129919   624961536    7  HPFS/NTFS/exFAT

   Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes
   255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
   Units = sectors of 1 * 512 = 512 bytes
   Sector size (logical/physical): 512 bytes / 512 bytes
   I/O size (minimum/optimal): 512 bytes / 512 bytes
   Disk identifier: 0x000f205c

      Device Boot      Start         End      Blocks   Id  System
   /dev/sdd1      1945524224  1953523711     3999744   82  Linux swap / Solaris
   /dev/sdd2   *        2048   976564547   488281250   83  Linux
   /dev/sdd3       976566272  1945524223   484478976   83  Linux

   Partition table entries are not in disk order
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1 Answer 1

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You don't really have hardware raid. You have what is known as fakeraid, which is just software raid that is implemented in a special driver to lie to Windows, and bios extensions to support the boot loader. Linux has no hacked up driver to do this, so the actual drives show up, but are also recognized by the dmraid package, which configures the device-mapper driver to perform the software raid functions. Ignore the individual drives, and the array should show up as /dev/mapper/something when you have the dmraid package installed. If you didn't install ON the raid array, then the dmraid package is not installed by default, so you will need to install it ( sudo apt-get install dmraid ). In order to resync the array now that it is mucked up, you will need to look for an option in the bios to scrub or resync the array, and boot into Windows until it is done, as this is generally not supported by dmraid.

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I installed dmraid, and rebooted. The array shows up as a single drive now when I view it in the file manager, and I did not have to scrub or re-sync. I imagine that this is likely what Ubuntu had enabled by default, (or at least something similar,) that I was missing in Xubuntu. Thanks for your help. I appreciate the easy fix to this. –  user229686 Dec 29 '13 at 19:33
    
@user229686, you need to scrub the array because if it is out of sync, and the primary drive fails, then the backup drive will be corrupt. worse yet, if the raid driver actually sends some read requests to the other drive when the first is busy to improve throughput, then reading may sometimes get different data depending on which drive the request goes to, and this will cause all kinds of corruption. –  psusi Dec 30 '13 at 4:10

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