Probably plenty of n00bish questions incoming.

I'm hoping some pedagogical person can take his/her time to read this :)

I am a complete unraid virgin. I just installed the trial version on my newly acquired server yesterday.

It is currently creating an array of my first eight disks. (6+2)

I have 24 total slots to fill up eventually, and ten more drives waiting (although eight of those have valuable data on them already from my old NAS. I have only had experiences with customer level NAS in the past.)

I took for granted that an "array" was simply like a raid array. You could create one array, select the drives and the redundancy, and then create another. Have several of these arrays, or "volumes".
But I am learning that this is not the case. An array, or should I say "THE array" is simply all the drives you want to store long term data, correct?

And then, what is a "pool"? I have understood people use it mainly as fast access cache using fast SSD's.

Does a pool need to consist of disks NOT in the array, or is it created from disks IN the array?

Does a pool have to contain a certain number of whole disks, or can it even be just a small part of a single disk?

And what about vdevs..?

My foundational question might be "If I want to store a file, I select a [what] to put it in?"

If the answer to questions like this is "rtfm", then I apologize. I just feel I need more of a visual mental image of how it's all connected.

And I have a feeling that if I just let the build of the array finish, and started tinkering on my own, I would get the hang of it after a while.

But, call me anxious... I would like to get a birds eye view early on.

Array and pools are two different things. Start by taking a look here, and if you still have doubts, ask questions:

https://docs.unraid.net/unraid-os/using-unraid-to/manage-storage/array-configuration/

https://docs.unraid.net/unraid-os/using-unraid-to/manage-storage/cache-pools/

Thanks a lot, stuff like that helps to get a fundamental understanding of the system.

So, there is only THE array, and you can make it as big as you like.

And there is a advantage og having a cache, as big and fast as possible.

My next question is, is two parity drives simply a question of adding security/integrity? Are there performance issues with having 20 data drives and 1 or 2 parity drives?

My initial thought was to add drives in chunks of eight, making 6+2 arrays as I going along.

But I could instead create a 22 data disk array plus 2 measly parity drives?

That would be awesome, as I would get way more data available.

Edited September 10, 2025Sep 10 by Abbe
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40 minutes ago, Abbe said:

My next question is, is two parity drives simply a question of adding security/integrity? Are there performance issues with having 20 data drives and 1 or 2 parity drives?

42 minutes ago, Abbe said:

But I could instead create a 22 data disk array plus 2 measly parity drives?

Yes.

The number of parity drives does not affect performance (once you have even 1), nor does the number of data drives.

42 minutes ago, Abbe said:

So, there is only THE array, and you can make it as big as you like

Yes within the limit of 28 data drives.

Support for multiple 'Unraid' type arrays is a roadmap item although we have no idea of the likely timescale for this support actually being released as it has been on the roadmap for quite some time. When that support arrives it will probably be treated as just another 'pool' type.

You can have multiple pools using either BTRFS or ZFS file systems. so that is another way of utilising extra drives.

45 minutes ago, Abbe said:

And there is a advantage og having a cache, as big and fast as possible

Note that 'caching' is technically a function associated with User Shares and reference a pool of any name (i.e it does not need to be called 'cache'). Its purpose is to act a staging post for writes to the array to improve perceived performance.

You might also want a pool to host docker containers and/or VMs with maximum performance. This can optionally be the same pool that you used for 'caching' but that is up to how you configure thins.

My plan is to have the two 2.5" bays in one redundant ssd-pool for containers/system files, and ill add a nvme pcie-card for the cache.

But just growing the array without worrying about additional stuff seems absolutely awesome :)

Edited September 10, 2025Sep 10 by Abbe