A few questions regarding hard drives and VMs

[formerflyboy]

Hi folks, I'm getting back into computers and networking after a looooong hiatus so this hypervisor stuff is new to me. After reading through a lot of posts and articles on the net i find I need to ask the forum a few things to clarify...

First, my setup is a Dell Poweredge r720 with 192GB RAM and 8x2TB drives configured via hardware RAID 6 (I also have 3 RPi in a server mount...lol). This gives me roughly 15TB of usable space presented as a single drive. I've also replaced the CDROM with a 250GB SSD that I install VMs on. The plan is to use the SSD for the VM software and the RAID drive for data. I've contemplated shutting off the hardware RAID and re-configuring to software RAID via Proxmox using ZFS but I've read that I would need to replace the PERC card with a non-RAID card. I'm just wanting to know if that's true or if simply not using the RAID function of the card is sufficient?

Question 2: At the moment I'm not sure if I've set something up less effectively than I should have but I have to manually pass thru the 15TB drive to make it usable for a given VM. Is there a way to do it once and make it permanent? This leads to my third question... For example, I have True NAS Scale installed with the entire 15TB drive allocated to it. I then install a VM that uses Ubuntu. When I allocate the same 15TB drive to the Ubuntu VM and it states it's going to wipe the drive, is it going to wipe out the contents of my NAS or is it only going to wipe the portion of the SSD that I allocate to the VM?

Thanks in advance for helping a "veteran newbie".

Jeff

 

[Dunuin]

Hi folks, I'm getting back into computers and networking after a looooong hiatus so this hypervisor stuff is new to me. After reading through a lot of posts and articles on the net i find I need to ask the forum a few things to clarify...

First, my setup is a Dell Poweredge r720 with 192GB RAM and 8x2TB drives configured via hardware RAID 6 (I also have 3 RPi in a server mount...lol). This gives me roughly 15TB of usable space presented as a single drive. I've also replaced the CDROM with a 250GB SSD that I install VMs on. The plan is to use the SSD for the VM software and the RAID drive for data. I've contemplated shutting off the hardware RAID and re-configuring to software RAID via Proxmox using ZFS but I've read that I would need to replace the PERC card with a non-RAID card. I'm just wanting to know if that's true or if simply not using the RAID function of the card is sufficient?

Depends on the card. You don't want any abstraction layer between the OS and the disks. All disks should be directly presented to the OS. If that card got a HBA mode that allows this it might be fine. But often the cards won't allow you to completely disable all raid, caching, monitoring and so on.
Depending on your PERC it might also be able to flash it from IR-mode to IT-mode to turn that PERC from a Raid card into a dumb HBA.

Question 2: At the moment I'm not sure if I've set something up less effectively than I should have but I have to manually pass thru the 15TB drive to make it usable for a given VM. Is there a way to do it once and make it permanent? This leads to my third question... For example, I have True NAS Scale installed with the entire 15TB drive allocated to it. I then install a VM that uses Ubuntu. When I allocate the same 15TB drive to the Ubuntu VM and it states it's going to wipe the drive, is it going to wipe out the contents of my NAS or is it only going to wipe the portion of the SSD that I allocate to the VM?

That is a bad setup. TrueNAS uses ZFS and ZFS shouldn't be used ontop of HW Raid. See here why: https://openzfs.github.io/openzfs-docs/Performance and Tuning/Hardware.html#hardware-raid-controllers
Best would be to get a HBA card, only attach your 8 HDDs to it and then use PCI passthrough to passthrough the whole HBA with all 8 disks attached to it into your TrueNAS VM. Then that TrueNAS VM will see those 8 individual HDDs, it can directly access the real physical disks and you can create your Raidz2 software raid inside the TrueNAS VM.

 

[formerflyboy]

Thanks for the info. That may explain all the problems I've had trying to get some things going. So I either need to get an HBA controller (any recommendations for one?) or choose another software solution. I guess since this IS a homelab I can try another software solution until I find and install a new controller card.

 

[Dunuin]

Without a dedicated HBA and PCI passthrough there is no way that a VM could access the real physical disks. Then you would need to run the NAS inside a LXC or bare metal directly on the host.