Why is it that SPAN and JBOD are the same thing?

[Ichinisan]

I would expect "SPAN" to combine several drives into a single logical drive. I would expect "JBOD" configuration to function logically as a standard drive controller (as opposed to a RAID controller) and present individual drives from the JBOD group to the system.

I was just reading some information about various RAID modes on Wikipedia and read that SPAN and JBOD are the same. I doubted this, so I googled a bit and found lots of other articles making the same claim.

It seems logical that a RAID controller would present to the system a "SPAN" group of drives as a single logical disk and a "JBOD" group of drives as individual disks.

Do any of you have thoughts on this?

 

[Zepper]

The whole idea of JBOD aka "a Spanned volume" is to present "just a bunch of disks" (any size drives) as a single volume without using the striping feature - JBOD may be a bit safer than RAID-0. If you want to see the separate drives, just don't use RAID features - most raid controllers work as standard controllers too.

.bh.

 

[Ichinisan]

Originally posted by: Zepper
The whole idea of JBOD aka "a Spanned volume" is to present "just a bunch of disks" (any size drives) as a single volume without using the striping feature - JBOD may be a bit safer than RAID-0. If you want to see the separate drives, just don't use RAID features - most raid controllers work as standard controllers too.

.bh.

That's just it. I would expect such behavior to be called "SPAN", and drives grouped in "JBOD" I would expect to be presented as individual drives on the controller.

To me, saying "just a bunch of disks" does not mean the same thing as spanning them into a single volume, but I think that hardware manufacturers and users on the Internet have changed the meaning.

 

[Zepper]

I think JBOD is just a catchy name for "spanned volume". I've never heard that it meant anything else until now.

.bh.