Comment by zaarn | Hacker News Reader

Comment by zaarn | Hacker News Reader

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One thing Btrfs somewhat promised was mixed disk RAIDs. Ie, having a 2TB disk and a 1TB disk and being able to say "keep 2 copies of any data in this subvolume" and "keep only 1 copy in this subvolume".

I'm currently on Bcachefs, which has erasure coding with similar promises and works better for me.

ZFS is more rigid, I have to have all matched disks for best performance, plus RAM unless I like bad performance (I don't). This could be solved by striping disks into 1TB partitions, but ZFS doesn't like living on a partitioned disk nearly as much.

Mixed disk has a bunch of cool properties for homelab users. Bcachefs also solves another problem; caching and speed. I could designate my 1TB NVMe as fast and my SATA 2TB SSDs as slow. I could also define that /tmp requiers no Erasure Coding and everything else requires 2 replicas. Then I would be able to combine the performance of my NVMe with the capacity of my SATA SSDs while gaining a simple redundance solution. My NAS has a dozen of mixed disks that I could combine more easily than ever.

The issue with ZFS is not that it's not ready to use. The issue is that it's born from enterprise and requires a costly enterprise setup to run, rather than a cheap homelab setup.

> but ZFS doesn't like living on a partitioned disk nearly as much.

Don't know how true is this, since it's not even possible to create a zpool on the whole unpartitioned device on linux. It automatically creates GPT label with zfs and a small efi partition.

That is true, but I suspect that only happens to protect the zpool against tools like the Windows Repair Install (which likes to attempt repairs on disks without GPT label). Using ZFS on a partition inside a GPT disk tends to lead to a few quirky behaviours, like for example ZFS not always reporting correct SMART data of the device.

IIRC ZoL `zpool create /dev/disk/by-id/ata-XXX` makes gpt partition table and zfs partition inside it.

A stub table.

It's nonsense. A ZFS pool is created from block devices, and ZFS doesn't care if those are whole discs or partitions.

Every ZFS pool I have is composed of GPT partitions, and this is also recommended in ZFS books as good practice to make it easier to identify a failed drive. Since you see the GPT partition name in the "zpool status" and other tools' output, it's handy.

On ZFS you can have multiple vdevs of different sizes in the same pool, and you can also set copies=N to have multiple copies of the data available for extra redundancy.

You can't unfortunately tell it that different disks have different speeds.

It also works just fine w/ a small (1GB or so) ARC if you want, just at an obvious performance penalty compared to having a larger cache.

ZFS cannot have different sizes in a single vdev and I'm tired of having to explain this to people everytime I mention this issue.

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