what is JBOD (Concatenation/Spanned)?

Discussion in 'Mac Accessories' started by Sossity, Feb 15, 2013.

  1. Sossity macrumors 6502a

    Joined:
    May 12, 2010
    #1
    what is this exactly? I saw this enclosure; http://www.icydock.com/goods.php?id=120

    among it's specs it shows this RAID type, when I saw JOBD, I thought that is was just a bunch of drives where each drive is seen and is independent. It looks like this JOBD combines the 2 drives together.

    I want a multibay enclosure with firewire 800 that among it's raid functions can use plain JOBD, not spanning/combining or anything.
     
  2. drsox macrumors 65816

    drsox

    Joined:
    Apr 29, 2011
    Location:
    Xhystos
    #2
    Read the blurb :

    " and thanks to a new concatenated JBOD mode, the user can have a combined storage volume without the risk for total data loss. The data is written across a single drive, and when it becomes full, it moves to the next drive, so if a drive fails, only the data on that drive will be lost "

    Must mean that a failure of a single independent drive still allows the other one to be accessible.
     
  3. Sossity thread starter macrumors 6502a

    Joined:
    May 12, 2010
    #3

    I am still a little confused, would I be able to set it up so the 2 drives are seen independently? would drive a show/mount as a single drive? and drive b a single drive? or would they both just combine as one drive a? I dont want them to combine as a single whole drive, but 2 independent hard drives.
     
  4. maflynn Moderator

    maflynn

    Staff Member

    Joined:
    May 3, 2009
    Location:
    Boston
    #4
    With JBOD you'll see a single volume that is the combined space of both drives.

    That is if you put two 1 terrabyte drive in a JBOD configuration, you'll see a 2 terrabyte volume
     
  5. drsox, Feb 16, 2013
    Last edited: Feb 16, 2013

    drsox macrumors 65816

    drsox

    Joined:
    Apr 29, 2011
    Location:
    Xhystos
    #5
    Depends on the options available. They say that their method is "a new concatenated JBOD mode" so maybe there is another selectable mode that is more traditional (i.e. not spanned and not concatenated). You'll have to get hold of the user manual to find out.

    See : http://en.wikipedia.org/wiki/JBOD#JBOD for the definition of normal JBOD.

    Looking at the user maunal (their spelling) : http://www.icydock.com/Installation Guide/MB662USEB_Maunal.pdf shows that there are two options - JBOD and BIG. JBOD might be traditional, BIG is concatenation/spanning. See page 5.
     
  6. flynz4 macrumors 68040

    Joined:
    Aug 9, 2009
    Location:
    Portland, OR
    #6
    Traditional JBOD would show each device as an independent volume... that you access independently.

    Concatenation (sometimes called spanning, or big) would combine them into one volume... but unlike raid... does not stripe nor mirror. It just fills data into the collection of disks.

    Some NAS vendors implement concatenation, but call it JBOD.

    /Jim
     

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