I am fairly new to Unraid and recently came into possession of a machine that will move forward as my home server for all things media, hobby and work.

The system came with 2 1TB NVME drives and room for more M.2's and 2.5/3.5" drives as needed. I have been using and setting up Unraid on one of the NVME's and I intend to use both as much faster data/cache for VM's, game server hosting needs, docker containers, etc. I just ordered one 8TB HDD to act as the bulk of the storage operations that will arrive tomorrow and I plan to order a second one in the near future.

I might be overthinking it, but what is my best course of action when introducing the HDD(s) into my Unraid environment? Parity is something that I want to prioritize. Do I add the HDD in, make it a disk share and then when I get my second drive use it to create parity with the other HDD? Do I just leave my NVME's out of it completely and stop letting them confuse me/this?

Based on my understanding of parity without having had a chance to use it yet, it would be with the NVMEs. Since they're only 1TB each and I'd love to utilize them both, my understanding thus far of parity is that I will "lose" one of them for the sake of redundancy, halving my available space on the small drives. This feels like a waste of a 4th gen PCIE NVME to me if so. Would I be able to both use the HDD for my storage needs described above while also using it as a parity device for the two smaller drives?

In an ideal world all general operations on the Unraid server would reference one or both of the smaller NVMEs nearly exclusively. Existing large media stores would sit cold on the HDD(s) until needed by plex or a docker container for example. New data too large for the NVMEs created in general operation would start on or be moved to the HDDs for cold storage/occasional reference. I would love if both the NVMEs and HDDs data was protected via parity, but I'm not sure of the best way to do that with the above storage scenario.

Any advice would be appreciated.

The general consensus is that SSDs should not be placed in the unraid array but in pools either mirrored or zfs raidz modes.

HDDs can either be pooled or be placed in the unraid array.

With that said your two NVME disks would be more appropriate for a pooled configuration and the 8TB HDD should be Disk1 in the unraid array. You'd want to get a 2nd 8TB HDD if you wanted to add parity.

See below, HDDs up top, SSDs at bottom. HDDs are single disk filesystems, the Cache pool is a zfs equivalent of RAID 10

Edited June 14, 20251 yr by MowMdown

I really appreciate your answer, this is exactly what I needed to know. My assumption is that this makes the HDD take over as the primary storage device for both system files installed by unraid to operate and for the uses I intend it for. Is there a performance cost for doing this?

To make sure I understand next steps when my 8TB HDD arrives in the mail, I'll describe what I think I'll need to do and someone can tell me how far off I am.

-Stop array and power server down

-Install HDD, power back up

-Use plugin to pre clear the HDD to prep it for use

-This is where it gets blurry but I know I've seen walkthroughs to transfer the current disk1 (one of the ssds) to the HDD and let it replace it as the primary disk of the array

-Once that is done, wipe/clear ssds and convert them to pool devices the way it looks above

-in a few weeks add the planned second 8TB and set it as a parity device with disk1 and plan on it taking some time for that process to complete.

Basically that’s the idea. Once the disk is ready to be added as the new disk1 you should be able to run a new config from the tools menu, put the 8TB HDD in disk1 slot and then put the SSD in the cache pool slot one. From there you should be able to move the data over to the HDD then add the 2nd SSD to the cache pool and redo the cache pool.

As long as you don’t format any of the existing disks you shouldn’t lose any data.

When you’re all ready just reach back out before proceeding.

Edited June 14, 20251 yr by MowMdown

I got the 8TB in, performed a config change and formatted the 8TB. I set the 8TB as disk1 and without making any other changes I put the NVME that was previously disk1 in cache pool 1 slot. When I started the array it fired up and showed the 262GB that was previously being used on the NVME as used on the HDD but there are no files present when I go and look and cache is showing 0 B used of 0B. I might be jumping the gun time-wise or I might not have performed a step properly. I see the 262GB being used by the 8TB as a good sign though.

I might know what I did. I'm making the change now but I might have put the previously unused NVME in the cache instead of the used one. I'll update if that's the case

Yes, that was it.

I believe I've worked my way through the data migration. Stopped the Array and mounted both drives via the UD plugin, went in and deleted empty pre-made folders on the HDD and then selected the SSD and am currently using the move function to transfer all files. What could go wrong, right...?

Sorry I didn't get a chance to check back in earlier. How did this go for ya?