# `[2026-09-01]` The Ada inference server is a Dell R750xa bought used — and the reseller stripped four things Dell shipped Dell PowerEdge R750xa, service tag **`JPJ1ZP3`**, 8-bay 2.5" 2U. Bought from Entera Source (invoice INV-74422, 2026-08-25). **2× NVIDIA RTX 6000 Ada 48 GB** to be fitted — confirmed by the operator, NOT L40/L40S. Destination NH3. This is ComfyUI's new home; the GX10 is a separate machine → [[2026-09-01-pfi-gx10-onboarding]]. ## As bought CPU 2x Xeon Silver 4314 16C/32T each = 32C/64T, 135 W each RAM 8x Micron 16 GB PC4-3200 = 128 GB NIC dual 25 GbE SFP28 (Broadcom 57414, OCP 3.0) boot BOSS-S2 + 2x 240 GB M.2 SATA, mirrored storage 2x 1.92 TB SATA SSD (Hynix), 6 of 8 bays free HBA PERC HBA355i (LSI SAS3816) PSU 2x 1400 W Platinum ## THE DIFF — factory CSV (`JPJ1ZP3.csv`, booth `54-puffin`) vs the invoice | | Dell factory | reseller invoice | |---|---|---| | **RAM** | **16× 16 GB `M04W6`**, "Performance Optimized" = **256 GB** | 8× = 128 GB | | **PSU** | **2400 W** redundant (`450-AJEV`) | 2× 1400 W (`7DWXY`) | | **GPUs** | 4× Tesla V100-32GB passive (`490-BHUC`) | none | | **GPU risers** | `12XPY` (right DW), `9TR6X` (left DW) | **not listed** | | **GPU cables** | `470-AEVS` 4-GPU kit: `4RW1P` `W4K7M` `XC48N` `6C77X` | **not listed** | | **Riser cables** | signal `CP67W` `CXYF8` `H4D7D` `N61TK`; power `HXJDR` `W1P56`; pad `C2JNP` | **not listed** | | **Fans** | 6× `FD00R` **Very High Performance** | **not listed** | | **CPU** | **2× Xeon Platinum 8362** 32C/64T, 265 W, **DDR4-3200** (`338-CCUS`/`W51V5`) | **2× Xeon Silver 4314** 16C/32T, 135 W, **DDR4-2666** | | **Controller** | PERC H345 | **HBA355i — an UPGRADE for us** | | **Drives** | 2× 480 GB | 2× 1.92 TB | ⚠ **"Not listed on the invoice" is not proof of removal.** Operator will pull an iDRAC inventory to settle it. Diff that against the CSV rather than the invoice. ⚠ **The CPU row was MISSING from this table until 2026-09-01** — the Silver 4314s were recorded under "As bought" but never diffed against the factory CSV, so the swap went unremarked. It has two live consequences: - **Memory speed:** Silver 4314 caps at **DDR4-2666**; Platinum 8362 ran 3200. The box **cannot use the 3200 rating** of the factory-spec `M04W6` parts on the buy list. Any DDR4-2666 RDIMM performs identically in this chassis as configured. ⚠ Verify the 2666 figure on Intel ARK before spending on it. - **Power, in our favour:** 270 W of CPU instead of 530 W. The ~1,020 W sustained figure below already assumes the Silvers and is correct as written. Cores went 64C/128T → 32C/64T. For an inference/render box that is largely irrelevant; noted so nobody re-derives it as a surprise later. ## The GPU power chain — resolved, and my first answer was wrong **RTX 6000 Ada: 300 W, ACTIVE cooling, one 16-pin 12VHPWR (CEM5) connector** (nvidia.com). The R750xa kit `470-AEVS` is **"W/CPU CONN"** — CPU/EPS 8-pin, because V100 takes that. I initially flagged this as a mismatch requiring the PCIe-type cable `RCCWC` / Dell `470-BBXH`. **That was wrong and is withdrawn** — `RCCWC` is for H100/L40/L40S. NVIDIA sells the bridge for exactly this case: > **`930-00030-1546-000`** — NVIDIA Power Cable, RTX 6000 Ada Generation, > **1× CPU 8-Pin → 1× CEM5 16-Pin** So the chain is `470-AEVS` CPU 8-pin → `930-00030-1546-000` → card. **The chassis' existing cabling is the correct source type.** Two adapters needed, one per card. ⚠ Factory brackets are `VFYGM` — the **V100S** extended bracket. RTX 6000 Ada is a different physical card; bracket fit is UNKNOWN, check at fitting. ⚠ **Active cooling in a passive-card chassis.** Six high-performance fans expect to push air through passive cards; the RTX 6000 Ada has its own blower. It works in practice, but Dell never validated this combination for this box. ## Storage — NVMe in the drive bays is CLOSED Factory backplane is `321-BGKG : 2.5" Chassis with up to 8 **SAS/SATA** Drives`. Not NVMe-capable; bays would need a backplane swap. Arithmetic if filling bays with SATA: 2x SATA (today) ~1.1 GB/s 6x striped ~3.3 GB/s <- roughly ONE NVMe drive 8x striped ~4.4 GB/s backplane ceiling ~6 GB/s (8 lanes x SATA III) The HBA355i (PCIe 4.0 x8) is nowhere near limiting. **Drives are the constraint.** **ARC probably beats spindles here.** ComfyUI reloads the same checkpoints; with the factory 256 GB restored, ZFS ARC caches most of the working set at RAM speed. The RAM upgrade is both cheaper and likely faster than four more SATA drives. ⚠ **CAPACITY, not throughput, is the binding constraint — the as-bought drives are SMALLER than the pool they receive from** (measured 2026-09-01). ComfyUI's `/storetank` on irv-ml1 is a 2x 2 TB mirror: SIZE **1.81 TiB**, ALLOC **1.45 TiB**, CAP **80%**. Settled payload **~1.47 TiB**. The R750xa's 2x **1.92 TB** mirrored is only **~1.75 TiB** — smaller than the source pool — so the migration arrives at **~84% full** with no growth room, past the ~80% line where ZFS allocation degrades. Compression buys nothing: safetensors measured `compressratio 1.00x`, `logicalused == used`. **-> Add 2x 2 TB SATA SSD to the buy list.** Six of eight bays free, HBA355i has the ports; two mirror vdevs = **~3.57 TiB at ~41%**, redundancy intact. Cheapest line on this buy list and it does not gate the cutover window. The no-spend alternative is striping the as-bought pair (~3.49 TiB, **no redundancy**) — only acceptable if irv-ml1 retains its copy, which makes retain a requirement rather than a recommendation. ⚠ **Pruning does NOT substitute for the drives.** comfy-dev found ~215 GiB of unreferenced weights; deleting every byte still lands the as-bought *mirror* at **72%**. The constraint is **vdev layout**, not payload — a 1.75 TiB pool stays 1.75 TiB whatever goes in it. The prune audit and the drive purchase are independent decisions. ⚠ **Build-time: pair like with like.** A mirror vdev caps at its smallest member; pairing each new 2 TB with an existing 1.92 TB caps both vdevs at 1.92 TB and wastes ~150 GiB. Correct: the two 1.92s as one vdev, the two new drives as the other. → [[2026-09-01-ada-migration-branch-a]] **UNCHECKED, and it may moot the whole bay question:** free PCIe slots. Riser Config 0 is `330-BBUM : Riser Config 0, 6x16 + 2x8 slots`; two double-wide GPUs will not consume all of it. An NVMe add-in card (U.2 HBA or bifurcating M.2 carrier) bypasses the SAS/SATA backplane entirely. **Add slot inventory to the iDRAC pull.** ## Power — the ceiling is deliberate now, not discovered later 2x RTX 6000 Ada 600 W 2x Xeon 4314 270 W rest ~150 W ~1,020 W sustained One 1400 W PSU carries that, so redundancy holds. But factory specced **2400 W** for four V100s: **there is no headroom for a third or fourth GPU.** And ~1 kW is the same class as ana-ml2, the box whose training run tripped a breaker on 2026-08-26 — **decide which NH3 circuit this lands on before racking, not after.** ## Buy list ⚠ **THE RAM LINE MAY BE FREE — operator has 2x Dell R640 with 768 GB each (2026-09-01).** Both are DDR4 **RDIMM** platforms (factory `M04W6` = `DIMM,16GB,3200,2RX8,8G,DDR4,**R**`), so the part class is the same 288-pin 1.2 V DDR4 RDIMM and Dell does not vendor-lock DIMMs. Three things decide it, in order: 1. **RDIMM vs LRDIMM.** 768 GB in an R640's 24 slots is almost certainly **24x 32 GB 2Rx4 RDIMM** — the safe case, drops straight in. If it is instead **12x 64 GB LRDIMM**, verify Ice Lake-SP / R750xa LRDIMM support first; do NOT assume it. 2. **Speed is a non-issue as configured.** R640 DIMMs are 2666 or 2933; the Silver 4314s cap the box at **2666** regardless (see the CPU note above), so 2666 parts lose **nothing** against the 3200-rated `M04W6`. ⚠ It WOULD become a cap if the Platinum 8362s were ever restored — the factory CPUs ran 3200. 3. **Slot arithmetic.** R750xa has **16** slots (8 channels/socket, 1 DPC); R640 has 24. **16x 32 GB = 512 GB — double the factory 256 GB spec**, and it kills the 8x `M04W6` line entirely. Cleanest harvest: **strip ONE R640 of all 24, use 16, keep 8 as spares**, leaving the second R640 whole — rather than half-emptying both into unbalanced populations. ⚠ **Confirm the actual DIMM part numbers from iDRAC or the DIMM labels before ordering anything.** And confirm the R640s are spares, not in service. **Certain (pending the R640 harvest above, which may delete the RAM line):** | item | part | qty | |---|---|---| | RDIMM 16 GB 3200 2Rx8 | **`M04W6`** | **8** → restores 256 GB. **Buy only if the R640 harvest fails**; 16x 32 GB from an R640 gives 512 GB free | | NVIDIA 12VHPWR adapter | **`930-00030-1546-000`** | **2** | | 2 TB SATA SSD (any; match/exceed the MX500s) | — | **2** → pool ~3.57 TiB at ~41%; without it the migration lands at ~84%. Pair the two NEW drives together, not one-each with a 1.92 | **Only if the iDRAC inventory shows them absent:** `12XPY`, `9TR6X`, `4RW1P`, `W4K7M`, `XC48N`, `6C77X`, `CP67W`, `CXYF8`, `H4D7D`, `N61TK`, `HXJDR`, `W1P56`, `C2JNP`, `FD00R` ×6. **Spend order:** **check the R640 DIMM part numbers FIRST (may zero the RAM line and double the RAM)** → RAM only if that fails → **SATA SSDs (certain, capacity-driven)** → check PCIe slots → only then consider filling the remaining bays. (The original order deprioritised drives on a *throughput* argument, which still holds; the drives are now on the certain list for **capacity**, which is a different axis.) ⚠ Dell's Installation & Service Manual publishes **no part numbers at all** for GPU kit hardware — names and quantities only. The factory CSV keyed to the service tag is the only authoritative source of DPNs for this machine. Do not accept a five-character DPN from anywhere else without corroboration.