Upgrading RAM on Synology DiskStation DS1621+

This is just a simple blog on how to upgrade RAM on the Synology DiskStation DS1621+ to better run Virtual Machines (VM) and Docker Apps.  Recently, I’ve upgraded my old Synology DiskStation DS1515+ to the new Synology DiskStation DS1621+.  The next steps are to upgrade the migrated HDDs from 5 to 6 as the Synology DS1621+ has 6 bays and also increase the amount of RAM of the Synology DiskStation DS1621+ so that my VMs can run more efficiently.  The Synology DS1621+ comes with 4GB of ECC SODIMM out of the box.  Synology has a comprehensive knowledge base article that talks about how to upgrade memory on their NAS.  Synology always recommends the use of hardware that cleared their hardware compatible list to ensure there are no issues of data corruption or server malfunctions.  Nevertheless, for this upgrade, I’ve reached out to friends at Synology and they have kindly sent over 2 x Synology 8GB DDR4 ECC Unbuffered SODIMM (D4ES01-8G) for me to test.

Side note: If you google enough on the internet, you can see posts or articles that talked about using other types of memory (even non-ECC ones) that the writers have tested themselves.  However, do this at your own risk as Synology will not warrant any issues caused by these non-certified accessories.


The Synology 8GB DDR4 ECC Unbuffered SODIMM (D4ES01-8G) is a DDR4 2666Mhz ECC SODIMM one-piece kit sold under the Synology brand name and comes with a 5 years warranty.  It’s a double-side SODIMM with 9 memory chips on each side but I can’t really tell the OEM of the chips used.  Each of these Synology 8GB DDR4 ECC Unbuffered SODIMM (D4ES01-8G) costs around S$252 on Amazon SG at the time of my writing.  This is certainly more pricy compared to other ECC or non-ECC SODIMMs but it gives users peace of mind as these memories are tested and certified by Synology.

Installing the new SODIMM RAM

Installation of the memory is very easy and straightforward on the Synology DiskStation DS1621+.  The RAM access door is at the bottom of the Synology DiskStation DS1621+ and removal of the two small screws and the access door will give us access to the RAM slots.  This is certainly much easier compared to the days when Synology used to put their RAM slot on the inside of the HDD bays.   I have to remove the existing 4GB RAM and install the 2 new pieces of Synology 8GB DDR4 ECC Unbuffered SODIMM (D4ES01-8G) in the 2 RAM slots.  In the future, if I do wish to further increase my RAM beyond this 16GB, I would need to go a new pair of 16GB SODIMM.


The Synology DiskStation DS1621+ booted up very smoothly after the installation of the new SODIMM RAM.  I checked the system information and it reflected all 16GB under the Physical Memory section too.  I boot up my Windows 10 Virtual Machine and noticed that it runs more smoothly and there is less swapping of the NAS storage.  One thing I noticed is that when I first boot up the Virtual Machine, the RAM utilization actually went beyond the 4GB of RAM I allocated to the Virtual Machine.  It actually went up to beyond 8GB (almost 60% utilization based on Resource Monitor) although I observed that I do not have other intensive loads on the NAS.  However, after a while, the utilization drops to around 25%.  I suspect this is due to the load on the Virtual Machine Manager due to the initial startup of the Virtual Machine.  I’ll monitor more and update here if I notice other things.


RAM upgrade to the Synology DiskStation DS1621+ is inevitable if you are going to use it beyond the role of a NAS for storage.  Going for Synology 8GB DDR4 ECC Unbuffered SODIMM (D4ES01-8G) is a more expensive investment but it’s not much compared to the value of data we keep in our NAS.  Hence do consider this when using third-party accessories.

After Note: I’ve been running the Synology 8GB DDR4 ECC Unbuffered SODIMM (D4ES01-8GB) on my Synology DiskStation DS1621+ for the past 6 months 24×7 without any failure.  The only time I need to restart was for planned maintenance or software upgrade.


Synology DS1621+ : Outside 5Synology DiskStation DS1621+: My new workhorse.


DS1621+ with stock configuration before any powerup

Synology 8GB DD4 ECC Unbuffered SODIMM (D4ES01-8G)

Synology 8GB DD4 ECC Unbuffered SODIMM (D4ES01-8G) – Box Front

Synology 8GB DD4 ECC Unbuffered SODIMM (D4ES01-8G) – Box Rear

Synology 8GB DD4 ECC Unbuffered SODIMM (D4ES01-8G) – Contents

Synology 8GB DD4 ECC Unbuffered SODIMM (D4ES01-8G) – RAM Itself Front

Synology 8GB DD4 ECC Unbuffered SODIMM (D4ES01-8G) – RAM Itself Rear

Synology DiskStation DS1621+ – Where to find the RAM Slots?

Synology DiskStation DS1621+ RAM slots with default 4GB RAM

Synology DiskStation DS1621+ with 2 x 8GB installed

Synology DiskStation DS1621+ with 16GB of ECC RAM installed

Installing Synology Virtual Machine Manager to run VMs on DiskStation

Setting up my PC into the first VM (with 8GB RAM) in Synology DiskStation DS1621+

RAM utilization before VM boots up

Performance of Synology DiskStation DS1621+ after VM boots up

RAM utilization after VM boots up

RAM utilization after VM shut down.  Noticed the 4.1GB of cached memory.

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