diff --git a/hosts/skydick/DATAPOOL.md b/hosts/skydick/DATAPOOL.md
index f9eb054..d5c069b 100644
--- a/hosts/skydick/DATAPOOL.md
+++ b/hosts/skydick/DATAPOOL.md
@@ -4,6 +4,10 @@
 
 Network: 10GbE bonded (bond0), jumbo frames MTU 9000, subnet 10.0.0.0/16.
 
+Pool: 9 × Seagate Exos/Mach2 ST14000NM0001 14TB SAS (4Kn), each presenting 2 LUNs.
+8 mirrors (from 8 drives) + 1 hot spare + NVMe SLOG/L2ARC. ~50.9T usable.
+See `datapool.nix` header comments for the full drive inventory and mirror layout.
+
 ## Available shares
 
 | Share | Server path | SMB name | NFS mount | Access |
diff --git a/hosts/skydick/datapool.nix b/hosts/skydick/datapool.nix
index a8c4537..9e2cfde 100644
--- a/hosts/skydick/datapool.nix
+++ b/hosts/skydick/datapool.nix
@@ -9,24 +9,35 @@
 #   LUN1: wwn-0x6000c500XXXXXXXX0001000000000000
 #   Same prefix = same physical drive. Pair DIFFERENT drives in each mirror.
 #
-# Drive inventory (ST14000NM0001, 14TB SAS Mach2):
+# Drive inventory (ST14000NM0001, 14TB SAS Mach2, all sg_format'd to 4Kn):
 #
-#   drive1: cab9587b  (serial ZKL09S4X...FA4P)
-#   drive2: caf74697  (serial ZKL05VPS...FMAC)
-#   drive3: cb3613eb  (serial ZKL05VM0...GSP3)
+#   drive1: cab9587b  (serial ZKL05VPS...FMAC)
+#   drive2: caf74697  (serial ZKL05VM0...GSP3)
+#   drive3: cb3613eb  (serial ZKL09S4X...FA4P)
 #   drive4: cb3957ab  (serial ZKL09QXG...50KE)
 #   drive5: cb9dd2eb  (serial ZKL0EP06...6LLW)  [spare]
+#   drive6: d76a9e4f  (serial ZKL0YA0X...4QB)
+#   drive7: d76aa413  (serial ZKL0Y9WR...31Y)
+#   drive8: d82293b3  (serial ZKL1FGTX...D63)
+#   drive9: d822944f  (serial ZKL1FGTM...63J)
+#   drive10: c9bcfa0f (serial ZKL01BH9...9J1)  [pending — sg_format in progress]
 #
-# Layout (4 active + 1 hot spare, all mirrors for expandability):
+# Layout (8 active mirrors + 1 hot spare, ~50.9T usable):
 #
 #   mirror-0:  drive1-LUN0  drive2-LUN0
 #   mirror-1:  drive1-LUN1  drive2-LUN1
 #   mirror-2:  drive3-LUN0  drive4-LUN0
 #   mirror-3:  drive3-LUN1  drive4-LUN1
+#   mirror-5:  drive6-LUN0  drive7-LUN0
+#   mirror-6:  drive6-LUN1  drive7-LUN1
+#   mirror-7:  drive8-LUN0  drive9-LUN0
+#   mirror-8:  drive8-LUN1  drive9-LUN1
 #   spare:     drive5-LUN0  drive5-LUN1
 #
-# If drive1 fails: mirror-0 and mirror-1 each lose one member, but stay
-# online via drive2. The spare auto-replaces one degraded member.
+# If driveN fails: the two mirrors carrying its LUNs each lose one member
+# but stay online via the paired drive. The spare auto-replaces one
+# degraded member. drive10 can be added as a spare or mirror pair once
+# its sg_format completes.
 #
 # === Pool creation ===
 #
@@ -42,6 +53,13 @@
 #     mirror wwn-0x6000c500cb3613eb0001000000000000 wwn-0x6000c500cb3957ab0001000000000000 \
 #     spare wwn-0x6000c500cb9dd2eb0000000000000000 wwn-0x6000c500cb9dd2eb0001000000000000
 #
+#   Expansion (2026-03-23, added 4 drives = 4 mirror vdevs):
+#   zpool add dick \
+#     mirror wwn-0x6000c500d76a9e4f0000000000000000 wwn-0x6000c500d76aa4130000000000000000 \
+#     mirror wwn-0x6000c500d76a9e4f0001000000000000 wwn-0x6000c500d76aa4130001000000000000 \
+#     mirror wwn-0x6000c500d82293b30000000000000000 wwn-0x6000c500d822944f0000000000000000 \
+#     mirror wwn-0x6000c500d82293b30001000000000000 wwn-0x6000c500d822944f0001000000000000
+#
 # === NVMe acceleration (Intel DC P4600 750GB, PHKE0163008K750BGN) ===
 #
 #   Partition:
@@ -135,10 +153,16 @@
 #
 # === Expanding the pool ===
 #
-# Add another pair of Mach2 drives (drive6 + drive7):
-#   zpool add dick \
-#     mirror <drive6-LUN0> <drive7-LUN0> \
-#     mirror <drive6-LUN1> <drive7-LUN1>
+# Add another pair of Mach2 drives (driveN + driveM):
+#   1. sg_format both drives to 4Kn if not already done:
+#        sg_format --format --size=4096 /dev/sdX
+#      Wait for completion (monitor with: sg_requests -p /dev/sdX)
+#   2. Wipe any leftover partition tables:
+#        wipefs -a /dev/sdX
+#   3. Add as mirror pair using stable WWN paths:
+#        zpool add dick \
+#          mirror <driveN-LUN0> <driveM-LUN0> \
+#          mirror <driveN-LUN1> <driveM-LUN1>
 #
 # === Service model ===
 #