How much main memory should a DS218+ need?

Plex Media Server NAS & Devices
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I’m having performance issues with LiveTV (artifacts, freezing, etc), even with hardware acceleration enabled for transcoding from a HDHomerun Connect. I’m wondering to what extent the fact that I have only 2GB of main memory installed is contributing to the poor video quality. In other words, would spending the money to upgrade memory likely improve the video quality?

I’m pretty certain the issue is not my home network since I have the DS218+ hardwired into an Orbi router and the Apple TV is hardwired into an Orbi satellite and the problems persist when the mpeg2vide streams are below 12 Mbps.

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We’re finding that the Synology boxes (J3355 and J3455 CPUs) do best with the full 8GB of memory onboard. The DS918+ comes with 4GB and the improvement by upgrading to 8GB (the other 4GB stick) is day & night better.

2GB really isn’t enough to run PMS, DVR, and DSM all at the same time.

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Thanks. According to the specs, the DS218+ can support up to 6GB (2+4 configuration). Should the 2GB currently installed be ditched and use 4+4 instead (even though 6GB is all that’s addressable)?

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The reason Synology states 6GB is because they install a 2GB module at the factory.

Simply buy 2 of the 4GB modules for it and replace the existing 2GB module.

My DS1815+ has the same ‘6GB’ limitation and is running just fine at 8GB :slight_smile:

The limit is what the CPU can address, which is 8GB

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Thanks @ChuckPa. I’ve ordered the memory. It may be a couple of weeks before I can install it and provide an update to this thread.

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In the interim, you can browse around at the DS918+ reports of others who’ve added memory. It’s quite remarkable .

I understand Synology’s point. They build and market a NAS. 2GB in a NAS is fine.

Adding Plex, with all its features, does need that extra room to work.

Based on personal experience, you’ll be pleased at the difference. Hardware transcoding “jumps to life” when it has enough memory to work freely

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I finally got around to installing an extra 4GB into my DS218+ (for a total of 6 GB).

First off, I now understand why Synology only advertises a max of 6 GB: in order to replace the existing 2 GB module, you have to take the whole unit apart to access the motherboard. I wasn’t ready to do that, so I decided to stick with 6 GB.

Before I installed the additional memory, I did have to do a reboot of DS218+, which actually helped with the performance issues considerably (though not completely).

After installing the additional 4 GB, performance seems to have improved, but there are still some TV channels that continue to glitch. According to then DS218+, this is happening when RAM utilization is only at 10-15% and CPU is hitting 30-50%. I tried using Channels for the same TV channel and it was able to transcode it without an issue (both Plex and Channels were using the same Chrome browser on a MacBook), which suggests the issue isn’t with the DS218+ hardware. Perhaps it has to do with the difference in the way the Plex handles the feed from the HDHomerun Connect?

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I am of mind to assert:

  1. They have a lot of 2 GB DIMMs around so want to use up manufacturing inventory.
  2. Certain newer models do get 4GB to start with (e.g. DS918+)
  3. The advertised 6GB limit is because the factory DIMM is 2GB and the max in any slot is 4GB.
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I’m by no means faulting Synology for their advertising limits and the fact that they start the DS218+ at 2GB (as you said (I think), it was designed as a NAS, not a video transcoder). But I must say I found it really surprising that they chose to make the motherboard DIMM so inaccessible (I checked out the DS918+: both DIMMs are easy to access).

But the issue I still have is the fact that RAM utilization is low and performance issues persist. Unless there is something strange with the way Synology reports utilization specs, there still seems to be a Plex software performance issue.

I probably should make it very clear that this is a very specific issue: Live TV for a few TV channels (that another app, Channels, does not have an issue with). Other than this relatively small issue, Plex is, in my opinion, a really amazing app, in so many ways.

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The specs on the Intel J3355 (the little brother to the J3455 used in the DS918+) are:

https://www.cpubenchmark.net/cpu.php?cpu=Intel+Celeron+J3455+%40+1.50GHz

It’s only 2145 Passmarks. Great for a NAS and running light applications. The only thing which makes it really viable for PMS and transcoding is the ASIC in the CPU. Most think of it as the GPU but it’s really a dedicated ASIC. The reason I encourage folks to use matched size & spec (matched pair) memory is two fold: a) Matched spec memory enables “Dual Channel memory mode”. ASIC and CPU can overlap operations on the memory bus. That’s a big plus when transcoding. b) Hardware transcoding needs the space. It’s reads memory from one block and writes the output H.264 to the other block frame at a time. If memory is contiguous, it’s considerably faster than if page faulting all over the place in the MMU

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That makes total sense to me: matched pairs are they way to go for maximum performance.

But my Channels app can do the transcoding without performance issues (it clocks in at the expected 1-1.04x), so the hardware configuration of my DS218+ can’t be the issue here.

@ChuckPa , I appreciate all your help on this: I have a much better understanding of the performance issues. But given the Channels app performance, I’m really not motivated to go through the trouble of replacing the motherboard DIMM to create a matched pair. Perhaps other DS218+ users can weigh in their experience with Live TV.

Thank you!

Andrew.

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I was fortunate. I only had to get two popsicle sticks to get the factory dimm out of the DS1815. It’s behind drive one. The access port is slightly greater diameter than the DIMM is long :slight_smile:

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