Use Dell H730 controller in pass-through for VSAN and RAID1 for VMFS simultaneously

[vihascoet]

Hello,

I would like to set up a vSphere cluster of 4 Dell R730xd using both VSAN for general purpose payload and RAID1 and/or RAID0 for special purpose payload (could be e.g. RAID1 for ESXi OS, or local VMFS over SSD for non-critical, High Performance payload).

The Dell H730 controller supports both RAID and non-RAID mode and is in the VSAN HCL, however, it is not clear to me whether the ESXi can use both modes simultaneously.

Also the PERC9 user's guide states that PERC 9 series of cards support two personality modes (RAID & HBA) and that "HBA mode should be enabled for customers, using Microsoft Storage Spaces or VMware Virtual SAN. HBA mode allows the operating system to control backplane LED functionality on supported systems." However, the HBA mode obviously doesn't allow for a mixed RAID/non-RAID configuration.

So here are my questions :

1. Will the intended set up work (controller in RAID mode, some disks in RAID, others in non-RAID) ?
2. What's the drawback of using disks in non-RAID mode rather than HBA mode, VSAN-wise ?

Any help will be greatly appreciated !

Cheers,

Vincent.

[zdickinson]

I don't think this is a VMware question, but rather a controller question.  Can you have the controller present some disks as a logical RAID drive and other ins HBA/pass through?  My guess is no, you have to choose whether or not the controller is in RAID or HBA/pass through.

I see two options.  Put the card into RAID mode.  Create your RAID 5 for example, and present that to the host to be formatted as local VMFS.  Then create the rest of the disks in RAID 0 for use in vSAN.  The downside is that if a disk failed in vSAN, you would have to down the server, remove the drive, re-create the RAID 0, and then have vSAN claim it.

Or put the card into HBA/pass through and use all the disks for vSAN.  You can now hot swap a drive in case of failure, but cannot create a local VMFS.

Thank you, Zach.

[DrewDeM]

So here are my questions :

1. Will the intended set up work (controller in RAID mode, some disks in RAID, others in non-RAID) ?
2. What's the drawback of using disks in non-RAID mode rather than HBA mode, VSAN-wise ?

1. Yes, I don't see why this wouldn't work.  I have used these controllers and you can specify the modes on each disk individually.  Though I wouldn't recommend doing it.  Especially not for your example of ESXi OS, that should just go on the internal SD modules.  

2. I haven't found any difference in running all disks in non-RAID mode vs HBA mode VSAN wise when testing previously.  The one place you might see a difference is if you decide to expand your hosts storage by adding additional disks you would have to configure the new disks as non-RAID. 

[zdickinson]

Thank you for the correction.  I agree it probably would work if you can set the mode on each disk, but probably not recommended.

On point two, I think you would still have the drive replacement difference between HBA/pass through and RAID 0.

Thank you, Zach.

[DrewDeM]

Hi Zach

On point two I'm not referring to drive replacement.  I'm referring to adding new additional drives. 

say you have a configuration with 2 groups

1 SSD 5 HDD

1 SSD 5 HDD

and you want to add disks to make it

1 SSD 6 HDD

1 SSD 6 HDD

With RAID non-RAID configuration you would have to go into the controller configuration\iDRAC and configure the new disks as non-RAID where as with HBA mode nothing would need to be done.

[vihascoet]

Thank you both for your answers,

As far as adding new disks in a RAID Mode is concerning, I understand this would not really be a problem since on new generation servers we can now edit the PERC configuration through the iDRAC8 while the server is running.

I agree ESXi should go on the SD card(s), this was not a good use case. However I still would like to be able to use RAID0 in order to agregrate SSDs for a striped VMFS (provided that the RAID0 overhead doesn't spoil the SSD performance...), and non-raid for VSAN, in which case the HBA mode is not an option.

Cheers,

Vincent.

[bseklecki_ge]

6 years later: The underlying technical question still remains:

Can the H730 have some drives in local/virtual disks, and some in Pass-through mode, and have VMWare access to both.

I will try (For another, similar, but not identical need)

[TheBobkin]

@bseklecki_ge No, mixing RAID (of any type) and passthrough on a single controller used for vSAN (+ anything else in addition to it) is not supported (though likely technical feasible but obviously do so completely at your own risk):

https://kb.vmware.com/s/article/53573