Raid Best practices

[JavierB]

I'm setting up an OpenMediaVault VM on which I want to create a RAID1 mirror made up of 2 IronWolf 4Tb disks.

What would be the best way to do it?

1- Install mdadm on the hypervisor, create the raid and perform a passthrough of the /dev/md0 to the OMV VM?

qm set 101 -scsi1/dev/md0

2- Perform a passthrough of the disks to the OMV VM, and then install mdadm for creating the raid under /dev/md0

qm set 101 -scsi1 /dev/disk/by-id/wwn-0x50014ee259e88552
qm set 101 -scsi2 /dev/disk/by-id/wwn-0x500003983588044b

Or maybe the best practice is different?

Thanks in advance!

 

[Dunuin]

I wouldn't use option 1 but should work too.

Option 2 will work but keep in mind that the VM won't be able to start, until you remove one passthrough from the VM, when one of the disks failed, even when the raid inside the VM would be fine because of the redundancy.

Option 3 would be to create some raid1 on the PVE host. ZFS as SW raid or HW raid with something like LVM-Thin on top would be supported. Not supported but working would be mdadm raid1 with LVM-Thin on top. Create a PVE storage to store VMs on it and then store a single virtual disk on it you then use with your OMV.
Here the benefit would be that the VM would be startable with a failed disk and that the VM would be migratable.

Option 4 would be to buy a HBA card and PCI passthrough the whole HBA with both disks attached to it into the OMV VM and then create your raid1 inside OMV. This is the only way how OMV could access the real physical disks without any virtualization (and its overhead/abstraction) in between.

 

[JavierB]

Thanks a ton!
I will go with option 2 as I can coexist if VM does not boot when 1 disk fails, and I have to remove it from the HW settings.

My disks are already using mdadm and I have no room to move existing data, so switching to ZFS is not an option for now.

Buying an HBA would be a good option, but too much for what I need.

I have an old DELL Optiplex 9010 for now, but sooner than later will be replaced by a MiniPC.. probably something like T-Bao R3

 

[Dunuin]

My disks are already using mdadm and I have no room to move existing data, so switching to ZFS is not an option for now.

Then keep the always repeated wisdom "Raid is not a backup" in mind. You should always have proper backups (yes, plural) of all data you care about so wiping the disks should never be a problem unless you only use to store some videos/music you could always rip again from your totally legal physical optical disks.