How does Unraid handle multiple different sized disks?

[mrme01]

I am looking to repurpose an old HP z800 as a storage box, I've been running Windows 10 on it, and it's built in Storage Spaces, the equivalent LVM for Linux. As I have moved to Linux (Debian) on my main machine, it makes sense my storage box should also run Linux.

Ideally, I am looking for something similar to Synology's SHR, where it can create a storage pool over multiple different sized disks, and the ability to both add and remove disks, and resize up and (hopefully) down to make use of all available space on attached drives.

I have tried virtualising DSM, but that leads to other issues. Other offerings like Truenas desire same sized disks and will only create a pool based on the smallest disk, IIRC.


With that said, can I achieve any of this with Unraid? Can I use all the space on different sized disks to create a storage pool with, and can that be resized with addition or removal of disks?

I am ideally looking to stripe, with parity.

Thank you for any information you can share with me, and feel free to ask questions on any detail I may have missed

[primeval_god]

2 hours ago, mrme01 said:

I am ideally looking to stripe, with parity.

The primary draw of unRAID is parity without striping. One way of thinking of unRAID is kind of like a JBOD with a parity disk (or two). Each disk (except parity) has its own complete filesystem, you can even be a mix of BTRFS and XFS disks. Parity is calculated in real-time over the raw disks and stored on dedicated parity disks. The user share system provides a unified (merged) view of the entire array and provides rules to control which disks files are written to. Individual files cannot span disks. With unRAID you can mix and match drive sizes with the only rule that the parity disk(s) must be as large or larger than the largest data disk in the array. Adding additional disks or replacing disks with large ones is easy (though you do typically have to stop the array for a short time to do so). Downsizing is possible but a bit more of a hassle (though not as much as other systems). At this time only a single unRAID array can be (and must be) created per server. Additional pools can be created using BTRFS (with BTRFS stripe or mirror modes), these are typically used for a form of new file write cache or to store application data.