Move RAID array from VM control to Proxmox control

[NickH]

Hi,
I have a 3 * 18TB disk RAID5 array on a Linux VM in Proxmox using mdadm. All disks are passed through to the VM and the VM OS controls the array. I now want to use some of the space elsewhere. I cannot set it up as an iSCSI target in the VM because port 3260 is already in use. There is > 8TB of data on the array and I don't want data loss.

My idea is to remove the three passthroughs and then do something like a `mdadm --assemble --scan` in Proxmox. Then mount the array in Proxmox to start on boot. I would then make the the new array an iSCSI target which this and my other VM can access. Note I do not want a remote iSCSI target connected to Proxmox. I want it inside Proxmox itself. I do not want to format the iSCSI target, but use it as it is as a single RAID5 partition.

Will this work? Will Proxmox be able to directly assemble the array and start it on boot.

 

[NickH]

Just for some closure, It more or less worked. I had to install mdadm into Proxmox. I removed the array config from the VM and the three passthrough disks and rebooted the VM. I then assembled the array in Proxmox and it worked fine. Initially I set up iSCSI to share the array until I found that iSCSI should not be used to share partitions at the risk of massive data corruption. I removed the iSCSI config and set up NFS instead and that is working fine. Speeds are not hampered by the network as it uses the Proxmox virtual bridge which is faster than 1Gb/s. Testing the NFS speed from the VM using dd to read and write 0's to a 10GB file on the NAS, I see > 200MB/s write speeds and > 400MB/s reads.

 

[tyler72us]

Just for some closure, It more or less worked. I had to install mdadm into Proxmox. I removed the array config from the VM and the three passthrough disks and rebooted the VM. I then assembled the array in Proxmox and it worked fine. Initially I set up iSCSI to share the array until I found that iSCSI should not be used to share partitions at the risk of massive data corruption. I removed the iSCSI config and set up NFS instead and that is working fine. Speeds are not hampered by the network as it uses the Proxmox virtual bridge which is faster than 1Gb/s. Testing the NFS speed from the VM using dd to read and write 0's to a 10GB file on the NAS, I see > 200MB/s write speeds and > 400MB/s reads.

This was super helpful trying to find a way to mount an existing RAID array in Proxmox. Spent a hour googling, so trying to add some keywords to help future searchers.