ZFS future ability to add different size disk?

[LIGISTX]

Hey guys! Not sure where to ask this, but I was reading up on - somewhere, can’t seem to remember where! - the potential to have different size disks in a ZFS vdev as a possible future feature. At least I think I read it correctly. It was a late night pre-bed on my phone read and I didn’t save the link and just forgot about until tonight.

I know synology and other file systems have the ability to do this, but ZFS does not. I can’t quite come up with the search terms to hunt this down again as the vast majority of results from any combo of “ZFS” and “different size disk” returns “no it’s not supported”. I just swear I read there is a possibility of it being introduced in a future version? Or it’s current being worked on as beta only? I can’t remember, just looking for info :)

*edit to clarify - I know you can use different size disks in a vdev with the restriction of the smallest drive size x n-drives being the limiting factor on vdev total usable space. Looking for info on combining different size drives in a vdev and using all of each of the drives space, while still maintaining parity; say a vdev of 10 4TB drives and 2 10TB drives in Z2, and having, well, some amount more than 40TB of formate usable space.

 

[sretalla]

You can mix sizes within a pool, but not a VDEV... (while making use of all space on all disks... as you mentioned, you can always do that if you assume you will get the least of the disks' capacity for all disks)

4x10TB in RAIDZ2 will work together with 4x12TB in RAIDZ2, for example, allowing the 10TB VDEV to use all of its potential and likewise for the 12TB VDEV. I think that's what you're asking.

Technically, it's possible to have different RAID/Mirror levels also, but mixing different types of redundancy in the same pool is to be avoided if you care about your data... RAIDZ2 together in the same pool with a Mirror can kill your pool with 2 disks lost in the Mirrored VDEV, whereas you might have thought you could safely lose 2 disks (which you can in the RAIDZ2 VDEV)... playing Russian roulette otherwise, but it's your choice.

 

[LIGISTX]

You can mix sizes within a pool, but not a VDEV... (while making use of all space on all disks... as you mentioned, you can always do that if you assume you will get the least of the disks' capacity for all disks)

4x10TB in RAIDZ2 will work together with 4x12TB in RAIDZ2, for example, allowing the 10TB VDEV to use all of its potential and likewise for the 12TB VDEV. I think that's what you're asking.

Technically, it's possible to have different RAID/Mirror levels also, but mixing different types of redundancy in the same pool is to be avoided if you care about your data... RAIDZ2 together in the same pool with a Mirror can kill your pool with 2 disks lost in the Mirrored VDEV, whereas you might have thought you could safely lose 2 disks (which you can in the RAIDZ2 VDEV)... playing Russian roulette otherwise, but it's your choice.

Yea I know that’s the current implementation, but I am sure I read about a future roadmap or beta to be able to add different size disks to a vdev and it would work out the parity distribution to allow for all space to be used while retaining the assumed redundancy of the RAIDZ level you chose.

 

[LIGISTX]

Maybe it wasn’t RAIDZ, but a different implementation still under ZFS?

 

[sretalla]

I am sure I read about a future roadmap or beta to be able to add different size disks to a vdev and it would work out the parity distribution to allow for all space to be used while retaining the assumed redundancy of the RAIDZ level you chose.

I don't think you were reading about ZFS. There are other filesystems that do things like that.

Maybe you're thinking about dRAID on ZFS? https://openzfs.github.io/openzfs-docs/Basic Concepts/dRAID Howto.html

Although that isn't what you were describing either.

 

[LIGISTX]

I don't think you were reading about ZFS. There are other filesystems that do things like that.

Maybe you're thinking about dRAID on ZFS? https://openzfs.github.io/openzfs-docs/Basic Concepts/dRAID Howto.html

Although that isn't what you were describing either.

Hmm. Possibly. I’ll take a look at that and see if that’s what I was remembering.

 

[LIGISTX]

Hmm, I think that is what I was referring to. But... I thought I had seen you can use different size drives and am not seeing that anywhere there or on some other results I googled. Maybe I misunderstood that part, or combined it with different info in my brain. Thanks for the link!

 

[danb35]

It's always possible to partition a disk, and use multiple partitions in a pool. Not really a good idea, mind, but possible.