Results 1 to 6 of 6

Thread: mdadm does not recognize USB 3.0 drives

Hybrid View

  1. #1
    Join Date
    Feb 2007
    Beans
    19

    mdadm does not recognize USB 3.0 drives

    I have a probox HD enclosure connected to my PC via USB 3.0. I can see the drives in the enclosure and I have put a gpt partition table on them (there are 4 3TB drives) and partitioned them. I even tried formatting one and putting files on it. which worked fine so I expect the drives are working.

    However when I try and create an array on them

    sudo mdadm --create --verbose --verbose /dev/md1 ––level=6 ––raid-devices=4 /dev/sdj1 /dev/sdk1 /dev/sdl1 /dev/sdn1

    it says

    mdadm: no raid-devices specified.

    Are the devices I am specifing not appropriate for some reason? I would assume that since I could partition and format them they would be alright but perhaps there some subltey I am missing here.

    I have spent several hours trying to puzzle this out and made little headway.

  2. #2
    Join Date
    Nov 2009
    Location
    Segur De Calafell, Spain
    Beans
    11,660
    Distro
    Ubuntu 12.04 Precise Pangolin

    Re: mdadm does not recognize USB 3.0 drives

    Are the partition types Linux Raid?

    Can you post the output for example of:
    sudo parted /dev/sdj print
    Darko.
    -----------------------------------------------------------------------
    Ubuntu 12.04 LTS 64bit & Windows 7 Ultimate 64bit

  3. #3
    Join Date
    Feb 2007
    Beans
    19

    Re: mdadm does not recognize USB 3.0 drives

    Here it is

    Model: WDC WD30 EFRX-68AX9N0 (scsi)
    Disk /dev/sdj: 3001GB
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt

    Number Start End Size File system Name Flags
    1 1049kB 3001GB 3001GB


    all four are the same with the exception of the last drive where I formatted ext4 just to see if it would work (it did). I figured that would get overwritten once I made the array and put a file system on it.

    Quote Originally Posted by darkod View Post
    Are the partition types Linux Raid?

    Can you post the output for example of:
    sudo parted /dev/sdj print

  4. #4
    Join Date
    Nov 2009
    Location
    Segur De Calafell, Spain
    Beans
    11,660
    Distro
    Ubuntu 12.04 Precise Pangolin

    Re: mdadm does not recognize USB 3.0 drives

    This partition #1 is not marked as raid. You see, the flags are empty.

    Try this:
    sudo parted /dev/sdj
    set 1 raid on
    quit

    That will set it as raid partition. After you do this on all four partitions/disks, try the mdadm --create again.

    But note that I am not sure mdadm will work on usb disks. How do you know the disks don't change places on each reboot? Are you sure they will be ordered in the same order?

    I remember another thread here with this same situation but it was a while ago and don't remember whether he got it working. I think not, not in a stable way anyway.

    Personally I wouldn't even think about software raid with usb disks. Not to mention the low transfer on usb, even on usb 3.0.
    Darko.
    -----------------------------------------------------------------------
    Ubuntu 12.04 LTS 64bit & Windows 7 Ultimate 64bit

  5. #5
    Join Date
    Feb 2007
    Beans
    19

    Re: mdadm does not recognize USB 3.0 drives

    usb 3.0 is supposedly faster than ESATA, also the drives show up with USB and not with ESATA, I guess my ESATA port multiplier doesn't work.

    Well I set the raid flag on all four partitions I can see it with parted. But when I run the mdadm to create the array I get exactly the same result as before.


    Quote Originally Posted by darkod View Post
    This partition #1 is not marked as raid. You see, the flags are empty.

    Try this:
    sudo parted /dev/sdj
    set 1 raid on
    quit

    That will set it as raid partition. After you do this on all four partitions/disks, try the mdadm --create again.

    But note that I am not sure mdadm will work on usb disks. How do you know the disks don't change places on each reboot? Are you sure they will be ordered in the same order?

    I remember another thread here with this same situation but it was a while ago and don't remember whether he got it working. I think not, not in a stable way anyway.

    Personally I wouldn't even think about software raid with usb disks. Not to mention the low transfer on usb, even on usb 3.0.

  6. #6
    Join Date
    Nov 2009
    Location
    Segur De Calafell, Spain
    Beans
    11,660
    Distro
    Ubuntu 12.04 Precise Pangolin

    Re: mdadm does not recognize USB 3.0 drives

    Well, if that didn't work, I guess you can't count on it working. I have no more ideas.

    As for usb3 speeds, or any usb external disk in general, theoretical speed is one thing, reality another.

    usb2 has speed of 480Mb/s which is 60MB/s. Have you ever seen a usb2 disk doing 60MB/s? I haven't.
    Darko.
    -----------------------------------------------------------------------
    Ubuntu 12.04 LTS 64bit & Windows 7 Ultimate 64bit

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •