Update docs: motherboard swap, NVMe cache pool, Docker migration

- New motherboard installed, MAC/DHCP updated
- 3x Samsung 990 EVO Plus 1TB NVMe cache pool (ZFS RAIDZ1)
- Docker migrated from HDD loopback to NVMe ZFS storage driver
- disk1 confirmed dead (clicking heads), still on parity emulation
- Hardware inventory, changelog, and incident report updated

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/incidents/2026-02-20-disk1-hardware-failure.md

@@ -2,7 +2,7 @@
 
 **Date:** 2026-02-20
 **Severity:** P2 - Degraded (no redundancy)
-**Status:** Open — awaiting replacement drive
+**Status:** Open — awaiting replacement drive (motherboard replaced, NVMe cache pool added Feb 24)
 **Affected:** XTRM-U (Unraid NAS) — disk1 (data drive)
 
 ---
@@ -21,6 +21,8 @@ disk1 (10TB HGST Ultrastar HUH721010ALE601, serial `2TKK3K1D`) has physically fa
 | Feb 18 19:17 | `super.dat` updated — md array marked disk1 as `DISK_DSBL` (213 errors) |
 | Feb 20 13:14 | Investigation started. `sdc` completely absent from `/dev/`. ZFS pool `disk1` running on emulated `md1p1` with 0 errors |
 | Feb 20 ~13:30 | Server rebooted, disk moved to new SATA port (ata5 → ata6). Same failure: `ata6: reset failed, giving up`. Clicking noise confirmed |
+| Feb 24 | Motherboard replaced. Dead drive confirmed still dead on new hardware. New SATA port assignment. Drive is mechanically failed (clicking heads) |
+| Feb 24 | New cache pool created: 3x Samsung 990 EVO Plus 1TB NVMe, ZFS RAIDZ1. Docker migrated from HDD loopback to NVMe ZFS |
 
 ## Drive Details
 
@@ -84,5 +86,6 @@ Mechanical failure of the hard drive (clicking = head crash or seized actuator).
 
 - Server is safe to run in degraded mode indefinitely, just without parity protection
 - Avoid heavy writes if possible to reduce risk to parity drive
-- The two NVMe SSDs (cache pool, ZFS mirror) are unaffected
+- New cache pool (3x Samsung 990 EVO Plus 1TB, ZFS RAIDZ1) now hosts all Docker containers
+- Old docker.img loopback deleted from disk1 (200GB freed)
 - Since disk1 uses ZFS on md, the rebuild reconstructs the raw block device — ZFS doesn't need any separate repair