QNAP Dual-Controller NAS Memory Upgrades
ECC memory for QNAP dual-controller NAS — the ES1686dc, ES2486dc, ES1686Adc, ES1686dc R2 and ES2486AFdc Enterprise ZFS systems. These units run two active controllers against shared storage, so a controller failure does not take the array offline, and that design shapes how you buy memory for them.
Both controllers get identical memory — the same number of modules, the same capacity, rank and speed, in the same slots — so either controller can carry the full load on failover. And ZFS wants RAM: QES holds its ARC read cache and deduplication tables in memory, so memory decides how the array performs under load. Every module on this page is registered ECC RDIMM, and every set is sold so you can order one identical set per controller.
The units on this page
| Model | Memory | Module sizes | Largest set we list |
|---|---|---|---|
| ES1686dc | DDR4-2666 ECC RDIMM | 16GB, 32GB, 64GB | 8×64GB (512GB) |
| ES2486dc | DDR4-2666 ECC RDIMM | 16GB, 32GB, 64GB | 8×64GB (512GB) |
| ES1686Adc | DDR4-3200 ECC RDIMM | 16GB, 32GB, 64GB | 8×64GB (512GB) |
| ES1686dc R2 | DDR4-3200 ECC RDIMM | 16GB, 32GB, 64GB | 8×64GB (512GB) |
| ES2486AFdc | DDR4-3200 ECC RDIMM | 16GB, 32GB, 64GB | 8×64GB (512GB) |
The ES1686Adc, ES1686dc R2 and ES2486AFdc use the Xeon D-2142IT and carry eight RDIMM slots per controller, up to 512GB per controller. The original ES1686dc and ES2486dc take DDR4-2666; the newer three take DDR4-3200. Check the installed modules before you add to them.
What "identical" means
Matching capacity is not enough. Two controllers at 64GB, one made up of 4×16GB and the other of 2×32GB, are not identical. Match the module count, the capacity per module, the rank and the speed, and install them in the same slot positions on both controllers. The simplest way to get there is to buy two identical sets at once — one per controller — from the same listing.
Sizing per controller
Each controller serves its own pools in normal operation, and in a failover it has to carry both, so size each controller for the combined load. Beyond the shipped configuration, the reasons to add memory are the usual ZFS ones: a larger ARC for bigger pools (a common rule of thumb is about 1GB of RAM per TB of pool), much more for inline deduplication, and buffer memory for busy iSCSI and Fibre Channel targets. If dedup is in the plan, size for it up front.
Population rules
- RDIMM only. These are registered-memory platforms. Do not mix in UDIMM or LRDIMM.
- Fill channels evenly. Populate memory channels with identical modules for full bandwidth; a partial upgrade that leaves channels empty costs performance on every controller it is applied to.
- Buy in pairs of sets. Every module count you plan for one controller is doubled for the pair: a 4×32GB upgrade on an ES unit is eight 32GB modules.
- Match rank as well as capacity. A 32GB 2Rx4 and a 32GB 2Rx8 are different modules. Order the upgrade from one listing so both controllers receive the same part.
- Use the speed QNAP lists. DDR4-2666 for the ES1686dc and ES2486dc, DDR4-3200 for the newer units.
Planning the upgrade
Dual-controller units are designed to be serviced one controller at a time; follow the controller service procedure in QNAP's hardware manual for your model. Have both sets on hand before you start and finish both controllers in the same maintenance window, so the two sides are never left with different memory.
How to check what is installed
- QES shows each controller's installed memory under system status and hardware information.
- QNAP's hardware specification for the model lists the slot count, the documented maximum and the QNAP RAM part numbers.
- The module label shows the capacity, speed, rank and the ECC / registered markings.
Ordering for deployments
Researched, matched, and compatibility-tested by NEMIX RAM, a US-based server memory specialist since 1993, and backed by a lifetime warranty. NEMIX RAM is a registered federal supplier (UEI GV8MMYNDJ5J1, CAGE 59AB2) and accepts purchase orders with net terms for business, government and education buyers. Send the model, the current per-controller configuration and the target capacity to our sales team, or request a quote, and we return one quote covering both controller sets. Volume and reseller pricing is available on request.
Frequently asked
Can I upgrade one controller now and the other later? Plan both together. Until both controllers carry identical memory, the pair is not in the matched state it is designed to run in. Buy both sets and do both sides in one window.
Can I add to the shipped modules, or must I replace them? You can add if the new modules match the installed ones in capacity, rank and speed and you do the same on both controllers. If the shipped modules are a different rank from what you are adding, replace the set.
DDR4-2666 or DDR4-3200? DDR4-2666 for the ES1686dc and ES2486dc; DDR4-3200 for the ES1686Adc, ES1686dc R2 and ES2486AFdc. Each listing carries the right speed for its unit.
Where are the single-controller enterprise units? The TS-h FU and FX all-flash units and the TDS-h2489FU are on the QNAP all-flash NAS memory page; every QNAP unit is in the QNAP memory by model collection.
See also: QNAP Enterprise NAS Memory · QNAP All-Flash NAS Memory · QNAP NAS memory guide · QNAP NAS Memory Cross-Reference
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