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what is JBOD (Concatenation/Spanned)?

S

Sossity

macrumors 65816
Original poster
May 12, 2010
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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.
 
Sossity said:
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.
Click to expand...

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.
 
drsox said:
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.
Click to expand...


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.
 
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
 
Sossity said:
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.
Click to expand...

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.
 
Last edited:
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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