We take cryptocurrency — so the coins you hold can buy real hardware.Pay in crypto, spend it on real hardware. Free insured shipping worldwide over $399. Plain, unbranded boxes, sent from Germany.Free insured shipping over $399. Your rate is locked for 30 minutes once checkout opens.Rate locked 30 minutes. Every item sealed, serial-checked and covered by a 24-month warranty.Sealed, 24-month warranty.

Saved items Sign in
Green circuit board with black memory chips and gold edge connector

Synology Inc.

Synology Inc. D4ES01-4G 4GB DDR4 ECC SO-DIMM memory upgrade

SKU CH-SHMF-7G24M MPN D4ES01-4G

4GB DDR4 ECC SO-DIMM module for compatible Synology 21-series NAS systems

  • Total capacity4 GB
  • Buffer typeUnbuffered
  • Product type260-Pin DDR4 SO-DIMM
  • Compatible systemsSynology 21 series: RS1221RP+, RS1221+, DS1821+, DS1621+
  • ECC protection guards data integrity on compatible Synology 21 series NAS
  • 4 GB capacity adds responsive multitasking headroom for demanding workloads
  • 260-pin DDR4 SO-DIMM form factor fits the approved memory slots exactly
  • Unbuffered design keeps latency low for snappy system response
  • Validated for RS1221RP+, RS1221+, DS1821+ and DS1621+ models

Synology 21-series ECC SO-DIMM

This 4 GB DDR4 module is built for Synology 21-series NAS units including the RS1221RP+, RS1221+, DS1821+ and DS1621+. It adds error-correcting memory to systems that support ECC, helping maintain data integrity during continuous operation. The unbuffered design matches the memory controller in these models.

260-pin DDR4 form factor

The stick uses the standard 260-pin SO-DIMM layout, so it slots directly into the memory socket on the compatible Synology mainboard without adapters. ECC circuitry works transparently once installed, and the unbuffered signalling keeps latency low for the workloads these appliances run. No extra configuration is required beyond seating the module firmly.

Upgrade from non-ECC or lower capacity

Owners of the listed 21-series units who currently run non-ECC memory or a single smaller module can install this kit to gain error correction and additional headroom. The jump is worthwhile when the NAS handles critical file services, virtualization or backup tasks where silent data corruption is unacceptable. Systems not in the 21-series compatibility list cannot use this module.

How it compares

Measured against everything we stock in Model-Specific Memory Upgrades, at today’s prices. Recalculated every night.

Price $67.99
Cheaper than about 73% of the 21,161 comparable items (median $397.99).
Total capacity 4 GB
Lower than about 90% of the 20,941 comparable items (median 32 GB).
Price per GB $17.00 per GB
Pricier than about 63% of the 20,941 comparable items (median $8.19 per GB).

New to this? Buying memory and SSDs with crypto — what to check, what it costs to pay, and what is never asked for.

Specifications

Product
Brand nameSynology
Part numberD4ES01-4G
Total capacity4 GB
Product type260-Pin DDR4 SO-DIMM
Memory
ECC supportYes
Buffer typeUnbuffered
Size & build
Shipping weight0.05 kg
Package size127 × 91 × 13 mm
Compatibility
Compatible systemsSynology 21 series:
RS1221RP+, RS1221+, DS1821+, DS1621+

Questions about this item

What DDR4 SO-DIMM standard does the 260-pin D4ES01-4G use, and what speed ceiling does that impose?

The module follows the 260-pin DDR4 SO-DIMM standard, so its transfer rate is limited by the DDR4 specification and the memory controller of the Synology 21-series NAS it is installed in.

Which physical slot and form factor must the NAS provide for this 4GB stick to seat correctly?

It requires a standard 260-pin DDR4 SO-DIMM slot, as found in the RS1221RP+, RS1221+, DS1821+ and DS1621+ models listed for the 21 series.

What is the correct insertion method for this ECC unbuffered module, and which step do installers most often miss?

Align the notch on the module with the key in the SO-DIMM slot, press firmly until the side clips click into place, and verify the clips are fully latched — the step most often missed is confirming both clips have engaged.

More in Model-Specific Memory Upgrades

Similar items