Moved disks to a RAID controller; can't bring back the software RAID5

  • Hiya,

    I have 4 drives of 2TB, previously connected directly to the motherboard SATA controller and configured in a RAID5 matrix under OMV. Recently I purchased a HP P410 SAS/SATA RAID controller for some extra kick. Today I connected the disks to the controller and ran into trouble: I can't bring up the RAID5 matrix for an unknown reason.

    The controller is configured with each drive in its own array and a single logical drive. Basically, it bypasses any built-in RAID functionality and exposes the disks as JBOD to the operating system. They just appear with a different name - instead of seeing their model, firmware etc. now I see "Logical volume" for all as Model.

    Here's what I'm getting:

    mdadm --assemble /dev/md127 /dev/sd[abcd] --verbose --force

    If I look in the system log, I get the following:

    I'm baffled, as I can check each drive with mdadm, but can't bring up the array. Any ideas, please?

    Here are some other results:


    cat /proc/mdstat


    Personalities :
    unused devices: <none>

    mdadm --examine /dev/sd[a-d]

  • Hm, or I could just connect those drives back to the on-board SATA controller, bring up the RAID5 matrix, and complete the data backup.

    The objective is to transfer the data from those drives so that I can set them up as a RAID5 matrix managed by the RAID controller card, and presented to the OS as a single volume.

  • Welp, I think I can mark this as "Solved" by applying the workaround above. Currently the 4 disks are connected back to the motherboard built-in SATA controller, software RAID working fine, and transferring data to other drives connected to the hardware RAID card. The sustained 70 MB/s copying speed is a lot better than 16 MB/s when backup disks were connected in a USB(2) external rack. Plus, the partitioning of those disks somehow messed up the partition table, so the backups were not actually retrievable :) So much for trusting USB racks.

    Tonight's fun: after all data is backed up, move the 4 disks to the RAID card and set up a RAID5 there. It has a specialized CPU for accelerating this, dedicated 512MB of ECC RAM, battery backup and a plethora of built-in tools for early identification and recovery from failures. Software RAID might be "free", but when a server-grade hardware RAID controller with all the bells and whistles is under €150... :)

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