Dell PERC and ZFS: can I avoid flashing it in HBA mode?

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Kurgan

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Apr 27, 2018
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I've been asked to consider buying a new Dell server that can work both with PVE and Vmware. Vmware requires a compatible raid controller, PVE requires NO raid controller (I want to use ZFS so I can make a ZFS replica to another identical server).

I know that modern PERC controllers can be set to expose disks in "non-raid" mode to the OS, even if the firmware is still the raid-capable one (so no need to reflash or buy a specific HBA-only controller). I understand that if we end up using PVE we have bought some high end raid controller that we will never actually use as a raid controller, so we wasted money... but the alternative is to buy a HBA and then have to buy a raid controller if PVE is not what management wants us to use, or if we encounter issues with the migration from the old Vmware to the new PVE.

Anyway, office politics and economics apart, can ZFS work on a PERC controller that has raid capable firmware but has the disks configured as "non-raid"?

Thanks.
 
i think the best option would be
for OS storage use a BOSS card with 2 m.2
For VM storage buy your perc card if you are planning to use local storage for vmware
Buy HBA adapters separately and swap out for ZFS testing

vmware does not require a raid controller, i think the majority of vmware customers are using BOSS/equivalent + SAN
 
AFIK most modern systems allow to change their RAID configuration via BIOS/UEFI settings. @Falk R. mentioned this several times thatthere is no need to risc breaking your PERC by flashing. So imho you should be good with a "non-raid" setting.
You can also use ZFS on HW RAID if you know what you are doing and it comes with some caveats like loosing some of ZFS features. I don't have any experience with such a setup though so I can't tell what you need to do for it.
 
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gasherbrum said:
i think the best option would be
for OS storage use a BOSS card with 2 m.2
For VM storage buy your perc card if you are planning to use local storage for vmware
Buy HBA adapters separately and swap out for ZFS testing

vmware does not require a raid controller, i think the majority of vmware customers are using BOSS/equivalent + SAN
Click to expand...

In our scenario vmware would be using local storage for boot and data, like PVE would. The difference is that Vmware needs a raid controller (an approved one, too), while PVE needs mostly anything that is non-raid to work. The idea here is to buy hardware that we can run with both software solutions, if it's possible. And a SAN is not the right solution for PVE.
 
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Not too old HPE Smartarrays (and most likely DELL Perc Adapters) should support mixed mode, if a drive is not in a raid array or configured as a jbod it is passed through to to os.
 
Johannes S said:
AFIK most modern systems allow to change their RAID configuration via BIOS/UEFI settings. @Falk R. mentioned this several times thatthere is no need to risc breaking your PERC by flashing. So imho you should be good with a "non-raid" setting.
You can also use ZFS on HW RAID if you know what you are doing and it comes with some caveats like loosing some of ZFS features. I don't have any experience with such a setup though so I can't tell what you need to do for it.
Click to expand...

Thanks, I definitely don't want to lose ZFS features by using it over a raid setup. If the controller can be completely bypassed by setting it properly and not flashing it, then it would be fine. Even better if I can actually have a hardware raid 1 for the OS and then a ZFS raidz-1 for data. This way I avoid having to eventually recover from a failed boot disk in ZFS, making it easier to recover a system with a failed boot disk.
 
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MarkusKo said:
Not too old HPE Smartarrays (and most likely DELL Perc Adapters) should support mixed mode, if a drive is not in a raid array or configured as a jbod it is passed through to to os.
Click to expand...
Yes, I understand this is the idea, and I have configured one like this already (one raid5 virtual disk and a single physical disk) in a different scenario. What I don't really know is if this is fine or has issues with ZFS.
 
Kurgan said:
can ZFS work on a PERC controller that has raid capable firmware but has the disks configured as "non-raid"?
Click to expand...
Since we don't have a Dell server this isn't the best answer, but on an old server with an LSI controller we installed PVE after breaking the hardware RAID and setting the SAS disks to JBOD. The OS sees the drive model/serial directly and the ZFS boot mirror is operating fine. It's been running PVE about a year. Typically in my experience a hardware RAID will show the RAID controller as the device model, to the OS. To me the linked ZFS doc doesn't mention JBOD/passthrough at all...closest is RAID 0 which is not the same.
 
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