Linux Admin Reference – Understand Device Mapper and DM-Multipath – Red Hat Enterprise Linux


I have started ( aka in 2009 as my own personal reference blog, and later sometime i have realized that my leanings might be helpful for other unixadmins if I manage my knowledge-base in more user friendly format. And the result is today's' You can connect me at -

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16 Responses

  1. pvprasanna says:

    i want to join with u

  2. Jerri says:

    I am actually delighted to glance at this webpage posts
    which contains plenty of helpful data, thanks for providing these
    kinds of information.

    • Ramdev says:

      Hi Jerri, Thanks for dropping the comment

      • Debu says:

        could you please explain, which raid is better software vs hardware raid and in real time companies are using software raid or hardware raid, with a real time example?(Disk replacement procedure in real time(solaris and linux)) and if raid then what is the need of hot spare pools ?
        I would really appreciate? As I have a lot of confusion on these topics??????

  3. Ramdev says:

    Hi Debu, Please check the link for quick reference on RAID – . Software. Hardware RAID simple to maintain but it has additional hardware .cost, most of the linux servers running on HP hardware normally use the Hardware RAID models. Where as Software RAID doesn’t require any additional hardware and completely management by software based volume managers like ( LVM in linux, SVM in solaris, VxVM …etc).

    below are the links that explains for disk replacement procedure in solaris ( configured with software raid using SVM ) –

    below is the link to configure software RAID in oracle linux —

    for hardware RAID, the setup is completely from System BIOS level.

  4. Debu says:

    Thanks ……..Good work……….
    please update some more realtime issues on linux ……….

  5. duraiarun says:

    hi Ram,

    how to maintain same device tree in two clusternodes in rhel 6.4

  6. Olivier says:

    Dude, thanks for the info, especially ALWAYS use /dev/mapper/mpathN devices !

  7. Gerald J says:

    Hey Ramdev,

    Great article.

    I have a system using multi-path. I note that the logical drives each get a /dev/md-* device node and I can see how they are related using the command:

    multipath -l

    But then each partition on each logical drive also gets a /dev/md-*. To see which partitions are associated with which /dev/md-* device nodes you can use ls -l /dev/mpath and follow the symlinks.

    So if you get an error message with a reference to /dev/md-xx and no indication of which partition that is you will be able to figure it out.


    Gerald J.

  8. TM Sundaram says:

    Very useful article. It contains valuable information’s.

  9. venkatesh says:

    Thanks for the excellent document. i have doubt in mapped table. in mapped table you mentioned start length…. could you please tell me what is length here. what i understood is length means the total size of the lv. is it right or wrong. if it is wrong could you please explain.

  1. April 9, 2014

    […] are some general links:…-dm-multipath/ […]

  2. May 26, 2014

    […] :    You Can refer  Understanding Linuce Device Multipath  and   Device Multipath Configuration in RHEL, for Basic Multipath […]

  3. June 18, 2014

    […] (from […]

  4. September 16, 2015

    […] Read– Device Mapper and DM Reference Guide […]

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