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Synology DS1618+ Homelab Review

This blog post is about replacing my Synology DS1515+ with a Synology DS1618+. I was forced to replace my Synology DS1515+ because it fell victim to the Intel Atom bug twice. The Synology is used for my primary storage in my VMware Home Lab.

This blog post is a bit later than expected to be honest… I already swapped out the Synology NAS about eleven months ago! So this is going to be a review based on my eleven-months experience and so information about why I bought the DS1618+ as a replacement.

Synology DS1515+ Atom Bug

In about six months two Synology DS1515+ past away in my Home Lab because of a hardware issue. One day they are working as they should and the next day you come home and they are dead. No lights, no sound, nothing is working “Bricked”.

The Synology DS1515+ is not a bad device… but it is using the Intel Atom C2000 CPU that is notorious for failing because it has an internal fault.

To get it clear it is not the fault of Synology… A lot of other vendors are also dealing with the Intel Atom C2000 fall out. Like Asrock, Cisco, HP, Netgear, Supermicro, and this list goes on. Here is an article from The Register with some more information surrounding this topic.

That is enough about the old let’s move on to the new!



Synology DS1618+ Setup

Here is an overview of the current Synology DS1618+ setup in my Home Lab environment. I have created two LACP bonds to load balancing iSCSI traffic from VMware ESXi on two dedicated VLANs.

  • Synology DS1618+ (default 4 GB memory/upgraded to 32 GB)
  • Storage pool 1: 2x Samsung EVO 850 500 GB – RAID 1
  • Storage pool 2: 2x Samsung EVO 860 500 GB – RAID 1
  • Storage pool 3: 2x Samsung EVO 860 500 GB – RAID 1
  • Network: 2x 1 Gbit LACP and 2x 1 Gbit LACP

All three storage pools represent a VMware Datastore and are made available with iSCSI to the VMware Hosts.

Here is an image that illustrates the current storage setup of my Home Lab environment. Nothing too fancy, all ports in the illustration are 1 Gbit.

Performance

Let’s start by looking at the Synology DS1618+ performance! An important aspect in my environment, it is not the size that matters but the speed!

Network

I have moved my SSD drives from the Synology DS1515+ to the Synology DS1618+ and the performance is identical… Say what? This is because the are limited to the same issue! Both devices are running against the network bandwidth limitation.

Both devices are out of the box delivered with 4x 1 Gbit network interfaces which can be easily matched by the three storage pools that I have installed.

Luckily the DS1618+ has an expansion slot, this is something the DS1515+ does not have! You can install a 10 Gbit network card which will improve the bandwidth drastically!

Memory

Already the memory issues/limitations in another blog post. Here is a reference to that blog post on my website.



Power Usage

Like all my Home Lab devices I like to know what the power usage is of each device. Synology indicates the following power consumption values on their website:

Factory measurementsWattage
Power Consumption – HDD Hibernation25.76 Watt
Power Consumption – Access 56.86 Watt

I have tested this with my power meter. In my case, the system was booted up and was supplying two ESXi Host with storage and a total of fourteen active virtual machines. The room temperature was 20 degrees celsius. I personally think 21.1 watts is not bad at all 🙂 surely compared to the DS1515+ that was using 25.3 watts with two drives less!

Tips

Here are some tips I have learned so far about the Synology DS1618+ unit:

  • If you are in need of performance install a 10 Gbit expansion card in the expansion slot of the DS1618+. Surely when using all-flash storage! This will easily outperform the out of the box network cards (4x 1 Gbit).
  • Install as much memory as you can in the device, this will reduce the disk swapping of the Synology OS and increase the performance and stability of the virtual machines running. Here is my blog post about this issue.
  • I have performed some tests with a cache drive that was an SSD device with a storage pool that was also an SSD device this did not improve performance (a maximum of about 5% in total, which is quite low if you ask me). If you are interested in a cache drive look at the NVMe expansion card but beware you only got one slot so… or you go with an NVMe expansion card or 10 Gbit NIC. So choose wisely depending on your requirements.

If you got some additional tips for people who are interested in a DS1618+ please respond below!

Sources

Here are some interesting websites related to the Synology DS1618+:

Synology DS1618+ Memory Expansion

After replacing the Synology DS1515+ with a Synology DS1618+ last year it was time for another investment in the Synology DS1618+. Overall it is a great device that is running my VMware iSCSI storage for my ESXi Hosts but based on some metrics the memory was experiencing some issues, so it was time for a memory expansion!

The reason why I am expanding my memory is physical memory swap usage. Based on my monitoring tooling the system is swapping to disk and when that happens the storage latency is increasing extensively on the iSCSI volumes (2500 ms / 2.5 seconds latency dips). The hypervisor and virtual machine survive but they don’t experience it as a good thing ;).

After a good session with a Synology Engineer on VMworld 2019 Europe, he explained that the storage latency I am experiencing multiple times a day must be caused by the swapping to disk and refreshing the read-cache in the physical memory. Synology is using physical memory as a read cache to boost performance by default.

Synology Statement

Here is the official statement from Synology surrounding performance and memory: “Memory usage remains high because the system stores frequently accessed data in the cache, so the data can be quickly obtained without accessing the hard disk. Cache memory will be released when the overall memory is insufficient. High swap space usage indicates insufficient system memory, and will also affect the system performance. You can view the rate of swap in and swap out by choosing Swap from the drop-down menu on the top.”

To clarify, my Synology DS1618+ is only running iSCSI storage with two volumes with both SSD drives in RAID1. The only services that are enabled are SSH, SNMP and off course iSCSI. The machine has no other purpose!



Memory Swap

The metric here is showing the usage of memory swap, the value 100% means it is completely empty, so no swap usage. The value 0% means that all swap is allocated/completely full.

As you can see in the graph there was always some swap activity going on in the last months around 92%. On 03-09-2020 / 03-10-2020 I installed the 32 GB DDR4 memory in the system and it is a steady 100% (so no swap in use).

Memory Expansion

I bought the following kit from Crucial 32GB Kit (2 x 16GB) DDR4-3200 SODIMM with the following part nr “CT2K16G4SFD832A“. This is the suited memory for the DS1618+ as you can verify on the Crucial website. The memory configurator tool can be found over here: Crucial Advisor Tool.

Luckily expanding the memory in a Synology DS1618+ is quite easy! I created a brief write-up and some photos are located below.

Procedure:

  1. Poweroff the VMware workload.
  2. Poweroff the Synology NAS.
  3. Remove the DS1618+ from his rack/shelf.
  4. Flip the device, the memory hatch is located on the bottom.
  5. Remove the two screws.
  6. Open the hatch.
  7. Remove the original memory.
  8. Install the new memory.
  9. Close the hatch.
  10. Install the two screws.
  11. Install in the rack.
  12. Power on the system (the first time booting will be longer than normal. The DS1618+ is performing a memory check, in my case, it took about 15 minutes).
  13. Power on workload.

Source

Here is the some additional links surrounding the memory expansion: