Hi all,
I’m running TrueNAS SCALE 25.10. Pool has one HDD data vdev (mirror, no RAIDZ) and one special/metadata vdev (2x 1TB NVMe, mirror). Metadata usage is only ~10GB, no small blocks configured, only metadata.
I want to replace the 1TB special vdev mirror with a pair of 200GB SAS3 SSD drives, since the 1TB capacity is way oversized for actual metadata usage.
I plan to add a new special vdev (2x 200GB, mirror) to the pool, then zpool remove the old 1TB special mirror, letting ZFS evacuate the ~10GB onto the new vdev.
Question: when a pool has two special vdevs and one is removed via zpool remove, does the evacuated data get written specifically to the remaining special vdev (preserving the special/metadata allocation class), or can the allocator spread it across other top-level vdevs too (including the HDD data vdev)? The zpool-remove man page just says data goes to “the other devices in the pool,” which doesn’t specify allocation-class targeting. Has anyone confirmed this behavior directly?
Thanks in advance,
Leo