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RAID 5/JBOD

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December 7, 2011 6:31:58 PM

I have a DNS343 and it offers a RAID-5/JBOD configuration. I understand what RAID-5 and JBOD are, but haven't seen them combined. Would this allow me to swap out the smallest disk in my RAID with a larger disk?

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December 7, 2011 7:06:54 PM

I've never heard of RAID 5\JBOD, but I would imagine that it uses the same to calculate parity storage as standard RAID5:

(N - 1) * Smin

N is the number of disks in your RAID set
S is the smallest disk in the RAID set. Obviously, you want all units the same, so use GB for large drives such as 1TB = 1000GB

So in this example, if you have
1TB, 500GB, 2TB, 750GB

Your formula would look like:

(4-1) * 500GB

Your total storage would simply be the sum of the disks so: 4.25TB

This means that the controller will carve out 1.5TB out of your 4.25TB RAID, leaving you with 2.75TB usable.

You should always be able to swap a disk as long as the replacement disk is equal to or greater than your existing disk.

So if your 500GB disk fails in the above example, you should be able to put in another 500GB or larger hard drive and the RAID will continue to function. However, this does not mean that the Virtual Disk will suddenly increase in size. Typically, although the replacement disk is larger, the controller will only use the space that was originally allocated when you setup the RAID set. In order to increase the size, you would have to rebuild the RAID.

With that being said, I've never heard of a combined RAID5\JBOD option!

Hope that helps!

December 7, 2011 7:24:52 PM

With the underlying logic drives the JBOD wouldn't the JBOD just resize it's self and the RAID5 would fit back on top of that, thus not having to rebuild the RAID?
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December 7, 2011 7:42:31 PM

I got that - and I know what JBOD and RAID5 are separately -- I'm trying to understand why D-Link 343 would have a combined JBOD RAID5 setup -- and have not been able to find any literature on how the two configurations work together.
a c 76 G Storage
December 7, 2011 8:22:27 PM

Nowhere do they claim support for both at the same time. In the description, they specify that RAID 5 requires 4 drives. That leaves none for JBOD.

1. Hard drive(s) not included. An internal SATA drive is required to store or share your files. RAID 5 requires the use of four (4) internal SATA drives. RAID 1 mirroring requires the use of two (2) internal SATA drives. To avoid data incompatibility in RAID 1 and RAID 5 operation, use SATA drives from the same manufacturer. Formatted drive capacity for RAID 1 and RAID 5 operation is dependant on the drive capacity of the lowest-sized drive. May not work with older generation SATA drives.
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