I’ve upgraded my TrueNAS SCALE installation to Electric Eel. I have a drive that I was using to import data that was from another Linux box that used mdadm mirroring. On Dragonfish I was able to utilise it by doing:
# mdadm --assemble /dev/md0 /dev/sdf1 /dev/sdg1
However, on 24.10, on running that I get:
modprobe: FATAL: Module md_mod not found in directory /lib/modules/6.6.44-production+truenas
mdadm: Fail to create md0 when using /sys/module/md_mod/parameters/new_array, fallback to creation via node
mdadm: unexpected failure opening /dev/md0
Has the required kernel support been removed? If so, was this deliberate or should I raise a bug for it?
Pretty sure it was deliberate. I don’t recall the exact specifics, but I think we ran into some cases where having it present was causing an issue with some certain setups when re-using disks from another system that had been previously formatted. Having it disabled fixed that so it didn’t have issues with pool creation IIRC.
If it was auto-detecting and assembling RAID arrays I can see why that would be a problem. Although, if that was the case I would have thought there would be other ways to disable it without needing to remove the kernel functionality / module.
I’ve been running Linux systems for over 25 years and personally I always enable swap unless I’m running off a USB key or similar device.
Anyway - I want to understand why mdadm based raid support has been removed. Having it is useful for recovering data from other devices, as well as using SMR drives that zfs dislikes.
