Dell Split Backplane Question

WinManX2000

New Member
Feb 28, 2022
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Hello-

I have been researching the storage solution for a Dell730 XD. I have almost decided to go with the split backplane 24 2.5 drive solution. This a dell solution that is designed to allow two PERC cards and lets you assign the front bays in groups to the different PERCS. You can choose 4:20, 8:16, 12:12, 16:8, 20:4 which are assigned to the physical drive slot.

I will have these 2 PERCS:
  • H730P
  • HBA330

Question:
  • If I assign the 1st 4 drives to the H730P and the remaining 20 drivers to the HBA330 via iDRAC, can I still pass the HBA330 through via the hypervisor? (I will be using proxmox)
  • I assume the answer is yes, but info is super limited.
This will let me setup a hardware RAID1 for the boot/OS/VM/IOCage and let me have 20 remaining to be linked to the HBA330 fully to truenas.

Thoughts?
 

oneplane

Active Member
Jul 23, 2021
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You can still pass either through to a hypervisor but it has to take any connected backplane and drives with it (it's more of a side-effect really - the entire PCI device gets passed and anything 'underneath' it comes with it).

There is a difference depending on how you configure the backplane; I don't completely remember how they configured the CPLDs on them but in most cases one of the cards has the configuration device on its bus and thus that is the only one that can configure the entire thing. After that, the data path just stays as-configured.

I mainly ran into this issue when converting a chassis to a disk shelf for additional bays during data recovery, some defaulted to a 'normal' or 'safe' 12:12 configuration but others defaulted to 0:0 and you get nothing attached until you provide the map to the backplane. In older versions it was even worse, it always routed all the connections to one card but then did a card-to-card map only to offload the RAID load and then tell the OS it should use the logical drivers on each card, not knowing they were actually not connected to one of them. This is something you can find out with lsscsi in Linux if you want to make sure of it ahead of time.
 

WinManX2000

New Member
Feb 28, 2022
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Wow. Sounds like you have actual experience here. So, I did specifically purchase it with a split configurable backplane. I have a pcie h730p and the hba330 mini module. I totally get that whatever ports are configured will pass as dummies. Where I was concerned was how the backplane can be configured in different splits if you will. Perhaps that is idrac speaking directly to the configurable backplane on how to route the sas connections and not through any perc module. Fingers crossed.