[SOLVED] Does it make sense to manage the virtual disks of a VM in RAID / ZFS?

WhiteTiger

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May 16, 2020
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Regardless of how the server's HDDs are managed, in hardware RAID or ZFS, does it make sense to manage the virtual disks of a VM with its own RAID / ZFS?
The performances would still be degraded, since they are always virtual disks, but how degraded? A lot or a few?
Obviously, the purpose of this disk management would not be to cover the risk of physical disk loss as much as damage to the virtual disk file and read / write performance (if any).
 

showiproute

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Mar 11, 2020
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I would say that it depends very much on your use case.
E.g. I had two separate & different HDDs - one was 4 TB and the other was 6 TB. I had no RAID setup on a hypervisor level.

I created two identically VM disks and used mdadm within my VM to create a RAID1.


What I would not do is to use ZFS on a hypervisor level + ZFS within the VM as this creates an unnecessary overhead.
 
Oct 7, 2019
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IMHO, using any kind of RAID or ZFS inside a VM is a bad idea (except for testing purposes, of course).

With your proposed configuration, If something breaks or fails is not easy to guess if the VM it self will be able to continue running properly. The OS may just see timeouts, CRC errors, the OS may just completely hang. The protection you may get for the disk files is lost for the data integrity inside the filesystems of the VM.

ZFS might help, but I just prefer to set disk redundancy Proxmox host(s), leave VMs as simple as possible and have proper backups.
 

Dunuin

Famous Member
Jun 30, 2020
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I also don't see the point using raid inside a VM. If you think virtualized SCSI isn't fast enough and you really need a super fast storage inside a VM it might be better to just buy a enterprise NVMe and use PCI passthrough to bring it inside the VM. That way you don't get the virtualization overhead, no other VMs will access that SSDs so the VM can't be slowed down by other VMs and you can make use of the throughput of the full 4 PCIe lanes.
 
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