Dell's Split-Backplane FlexZone Feature | TechMikeNY



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Dell’s Split-Backplane (FlexZone) Feature. What is it? A Primer, Use Cases, and Resources for Implementation


What if there was a solution available where you could have two separate RAID arrays in a single server, controlled by different RAID cards, with lightning-fast speeds between the two disks? 

If that sounds like an appealing solution to your server environment, then let us introduce you to Dell’s Split Backplane Mode (or FlexZone) functionality.  This rare tool in specific Dell servers allows you to have two PERCs – or a PERC and then a 3rd party RAID controller – in one server. 

This post will cover the basics of Dell’s Split Backplane, who might benefit from its implementation, and how to set it up – or turn it off – in your compatible Dell server. 

TERMINOLOGY PITFALL!  Don’t confuse “FlexZone” – Dell’s split backplane feature – with “FlexBay.”  “FlexBay” is a feature in some Dell servers which allows you to house an additional number of drives in the front of the server (usually x2 2.5” drives). 

The Basics of Dell’s Split-Backplane FlexZone Feature

Whereas the vast majority of Dell servers mandate you to have all your drives controlled by a single RAID card – whether a mini-PERC, PCIe PERC, or 3rd Party PCIe card – servers with Dell’s split backplane mode allow you to have TWO RAID cards.  In turn, those two distinct RAID arrays are managed by each controller.

The key advantages to this hardware topology are the ability to have essentially two RAID disks in one machine and the two disks to share data at breakneck speeds since they are transferring between the server’s integrated SAS cables.  (A helpful analogy could be to virtualization: when you create a VM, you essentially have a computer-within-a-computer.  With a split backplane configuration, you can create two storage arrays in the same server – virtually two solutions in one!)

With this in mind, there are a couple of key points:

  • For the 13th Gen Dell servers, ONLY the following servers can engage split backplane functionality (since the assumption is only high quantity drive machines would benefit from having two distinct arrays managed by a separate RAID card):
    • R730XD 24 bay
    • R730XD 12 bay
    • R630 24 bay (1.8” drives)
    • R630 10 bay
    • R920, R930 (we don't have extensive experience with R900-series servers, but it is a 4U machine with a high amount of drive bays).  
  • In Split Mode, admins can run the PERC in RAID or HBA (passthrough) mode.

Use Cases?

Now that we’ve covered the basics, what are some of the advantages, or use cases, that FlexZone might be beneficial?  While this isn’t an exhaustive list, it should give you an idea of the advantages and functionality of the split-backplane mode.  Let’s dive in!

Two RAID arrays in RAID 0.  RAID 0 improves the collective performance of drives in an array, treating them as one volume.  While you gain speed, RAID 0’s Achilles Heel is no backup or redundancy with the virtual disk.  If you lose one drive – the whole VD is gone!  With a split-backplane solution, you could conceivably have TWO RAID 0 disks, and should one fail, the other VD in the same machine is ready to jump into action.

Two RAID arrays – one is a PERC, the other is a 3rd Party RAID controller.  One of the challenges to utilizing a PERC controller is the data is stored in a proprietary format (in other words, if you want to move the disks of that RAID array, you need to move it to a machine that is using a similar – if not identical – PERC).  With the split-backplane mode, you could have a RAID array managed by a PERC and another array in that same machine operated by a 3rd party (non-PERC) controller.  You have the same array, but not limited by the RAID controller brand, should you need to move it to a new machine. 

HOT TECH TIP!  Two RAID arrays in the same server, configured with Split Backplane Mode, cannot connect without an OS!  While you can configure the RAID VDs in iDRAC, the data would not be shared between the drives.  Should one of the controllers fail, the data would not automatically pick up the data without an OS managing the connection.  

How to Turn On Split Backplane Mode; and How to Turn It Off (or Unified Mode)

Dell has various valuable resources on their support pages about the different configuration flavors of split-backplane drives you can implement (i.e., X number of drives on the first controller; X drives on second) and how to turn on these features through iDRAC or RACADM. 

  • For Dell’s high-level background for configuring iDRAC v7 & 8 for split-backplane, click here.
  • For configuration through iDRAC web interface, click here.
  • For configuration through RACADM command prompts, click here.

CHECK OUT OUR OTHER RESOURCES! To read more about RAID, check out our blog post here. To read more about Backup Best Practices, check out our blog post here.

Final Thoughts

The split-backplane feature is a tool that we’ve noticed many of our customers aren’t very familiar with.  That’s why we decided that sharing our knowledge of the tool would be helpful – it’s what we’re here for!

As always, if you have questions, concerns, or a general support inquiry, email us at    


  • Chris, thanks for the comment below. For whatever reason, we almost never receive any R900-series servers in our reseller pipeline. So we are extremely unfamiliar with that model’s features and architecture. That said, we’re going to add it to the post. Thanks again for the catch! P.S. I did a quick look at the R930 specs, and it looks like that model supports Split Backplane as well.

  • Split mode is also supported on the Dell R920.

    Christopher E Young

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