Unraid, Cache, and Windows 10 VMs | Best Practices?

[Nickatlm]

Hello all,

 

Forgive my ignorance, I'm new to unraid.

 

I'm working on testing a proof of concept setup, I'm trying to run a Windows 10  VM in Unraid 6.4.1 on a Storinator Q30. The goal is to run camera system software on the VM and have it store all the footage on a large virtual disk stored on the array.

 

What is the optimal way to configure 10x 12TB Western Digital Gold HDDs and 1x 128GB SSD to support a VM that will potentially have 1Gbps of traffic flowing into it 24/7

 

The array is set up to use 2 of the 10 drives for parity. I added the SSD as a cache drive and I set up a share on the array. I set the "Use Cache Disk" to "Yes". I installed the VM on a 50GB virtual disk and attached a larger 20TB virtual disk as well. The virtual disks were placed on the share I created earlier. I installed the camera system software and set up 1 camera on it.

 

Everything ran fine for a few days until the VM started pausing intermittently and I've been unable to figure out how to stop it from happening. From what I've read its probably caused by either power settings on the VM or its related to my cache disk being full.

 

I've changed power settings on the VM to "High Performance" and "never sleep" and set the "Use Cache Disk" setting on the share to "No". I also removed the installation .iso and virtio.iso from the VM since the are located in shares on the cache disk (by default).

 

I'm guessing the virtual disks are still being cached because changing the "Use Cache Disk" setting  to "No" only affects new files.

 

Also:

The array is fast and according to the speed tests I've done its more than capable of receiving that much incoming traffic but what about the cache disk? Won't pushing that kind of traffic through a single SSD burn it out quickly? Should I even be using a cache drive?

 

Any input is welcome. 

 

Thanks,

lmc-arc-01-diagnostics-20180404-1117.zip

[JonathanM]

It sounds like you are running out of space on your VM's virtual disks.

 

I know this sounds crazy to you based on what you think is happening, but unraid doesn't work like you think it does. Each 12TB data drive is an individual file system, as is the cache drive. The user share that spans those drives is only a virtual overlay of the individual drives, so you can't make any single file take up more than one drive. You created a 20TB disk image file, which was created successfully because VM disks are sparse by default, they only take up as much space as they have data, and expand as needed, while showing as the full size to the VM. So, as you filled that 20TB, it worked fine until it bumped up against the hard constraint of the 12TB physical drive, or the much smaller cache drive.

 

To accomplish what you originally set out to do with one contiguous volume spanning multiple disks, you would need to use the windows disk management to concatenate multiple VM disk images, each on one of the data drives. I don't know how that would effect performance. Multiple separate volumes, mounted to unique spots in the VM would probably perform better.

 

The cache disk doesn't work like you are thinking either, at the moment I don't know where you are actually writing data, but I suspect both your image files are on the cache drive, and nothing is on the array. If you click on the folder icon to the far right of each disk on the main GUI page you can view the files that reside on each of the disks.  

[Nickatlm]

Ahhh, that makes sense,

 

Yes, the reason my VM is pausing is because my image files are on the cache drive. I see that now.

 

You've also saved me from a major headache down the road. If I had rebuilt everything without using cache the vm would have become unusable as soon as the 20TB image hit around 12TB full.

 

I'll probably end up going with a more traditional setup using Windows Server and some hardware raid cards since I'm not super excited about the idea of creating 8x 10TB image files, attaching them all to the VM, and striping them together with a windows software RAID.

 

Thanks for your help!