So I’ve decided to reclaim my 5k iMac as an actual computer, and not a 24/7 media machine. I purchased a Synology DS918+ diskless, and 16GB RAM upgrade (Crucial). It should be arriving on Thursday, so I have some questions…
KNOWNS:
I will be using a Synology DS918+
It will have 16GB of RAM
It will have 4 x 4TB HDD’s
It will be used solely for Plex…and maybe Infuse (questionable)
It will have less than 8 users including myself, with at most 2 people using it at the same time
All movies/tv shows are encoded to MP4(SD, 720p, 1080p) and AC-3 (stereo if old/no other choice)
I’ll eventually start to add 4K HDR material
QUESTIONS:
As it’s PRIMARILY being used for Plex and Media serving, will adding 2 x 256GB WD Black M.2 NVMe into the mix for caching purposes do anything for Plex?
Has the bug/glitch with 16GB ram upgrade <=> SSD Cache UI been fixed?
Does Plex or the NAS, or both, benefit from the additional RAM if only used for streaming?
Are NAS grade HDD’s absolutely essential for my use case? Users, myself included, aren’t accessing this 24/7.
And, related to #4, if not essential…am I safe buying great desktop grade HDD’s with a lower rated RPM for [READ] “sustained” performance?
2 x 256GB of M.2 will only server as disk i/o cache. It will serve no other purpose
What ‘bug’ ? Just because Synology reports the total of the sizes reported by the DIMM SPD chip, doesn’t mean it’s usable.
Hardware transcoding benefits the most. This is why it’s recommended to upgrade the processor to 8GB of RAM.
If you don’t use NAS grade, proceed at your own peril. They exist for a good reason, primarily heat and vibration.
NAS grade drives, unless purchasing PRO drives, are 5400. Reading 100 MB/sec gives you 800 Mbps of video from a single drive. Spread this across the array which gives you 300-400 MB/sec and you now have 2+ Gbits/sec even at a paltry 100 MB/sec. Old desktop WD 2003 Black drives were rated at 120-140 MB/sec. New NAS drives are even faster
I’ve been seeing on a lot of forums (this one included) that some users of this device have successfully installed 16GB and utilization reports the increase as well. And also that the J3455 supports 8GB per channel and not total. And for some odd reason, NewEgg sells this unit preconfigured with 16GB as a choice.
I’m not at all saying you’re wrong or right. But now I’m confused.
Also the M.2 serving as I/O cache for the system would…cache frequently accessed files for faster retrieval/playback for Plex? Or just general server stuff?
I know what people say and, frankly, it’s incorrect. Is it really likely Intel is going to get the tech specs wrong for its processors and not have somebody scream? Extremely unlikely. It’s far more likely for Synology to have overlooked one possible configuration in software memory size reporting.
Synology will report 16GB because 8 + 8 = 16. The BIOS queries each DIMM. It gets 8GB from the first and 8GB from the second. it adds the values and reports 16GB. That’s how it shows up. Granted, Synology could have addressed that but they didn’t. Botttom line, the processor cannot address it. Dual channel operation is not “8 gig on this side, 8 gig on that side”. Dual channel is two overlapping memory transactions at the same time, one read & one write. It’s a function of the memory controller utilizing otherwise idle memory bus cycles perfectly interwoven.
The M.2 as cache on Synology will cache everything. There is no control of what does or does not get cached. Caching is done at the Volume level of granularity
Your best bet is to get an 8GB Kit (a matched-spec pair). They have been tested to operate so close in timing the CPU will see them as ‘good enough’ and enable dual-channel mode.
@ChuckPA: So an 8GB (4+4) kit will provide some (small to ???) benefit over a 16GB (8+8) kit? B/c the 4+4 will allow for dual-channel but with the 8+8 kit half will be ignored (e.g. slot 2)? Or is having 8 on one stick by itself faster than 4+4. I’m sure we’re talking milliseconds here anyway
You are correct. The second 8GB stick can’t be addressed by the processor.
Since it can’t be addressed properly, dual channel mode doesn’t engage. Dual channel mode is what allows overlapping memory operations. It’s not possible to overlap memory ops with only one DIMM.
The obvious question is: What benefit is it to Plex on the Synology with the J3455 or any Intel QSV-capable CPU?
The J3455 CPU is actually TWO processors in addition to the GPU.
The CPU and attached GPU
The QSV co-processor (ASIC)
If you read this article, https://en.wikipedia.org/wiki/Multi-channel_memory_architecture , you’ll see the architecture and the theory of why it’s beneficial. You’ll also see the modest (5%) gains obtained from overlapping CPU-intensive memory operations only. It makes no mention of co-processors but we know of the huge gains with multi-channel memory when multiple CPUs are on the same motherboard. This is why quad-channel mode exists… 4 CPUs per motherboard for server platforms.
Now enter the QSV ASIC and transcoding and Plex.
We see the CPU running at 3-4% load while the ASIC (most call it the GPU) is doing the transcoding.
The CPU and ASIC are sharing the bus and not interfering with each other because of that dual channel mode. Dual channel mode has doubled the available memory bandwidth (not clock speed or rate) and hardware transcoding is a pure memory-to-memory operation. The CPU is free to transcode the audio and run PMS while the ASIC is being handed memory blocks to transcode by the transcoder.
In summary. 4 + 4 is the maximum benefit you’ll get from the system because that’s all the address pins it has coming out the bottom.
Edit: Think of dual channel memory like striping two identical size disks. It screams
Actually, more than 8GB RAM in the DS918+ just works, regardless of what Intel’s spec sheet mentions (yes, that surprised me too). It’s not just that DSM reports the memory size, but I’ve taken it to >80% memory usage running virtual machines and docker containers without any issues.
I can’t judge whether it’ll run in dual channel configuration, but it probably won’t, so 2x4GB may be faster if you don’t need more than (or close to) 8GB. Plex doesn’t seem to use that much memory anyway so in OP’s case, 2x4GB would be the way to go.
Since 8GB doesn’t cut it for what I want to do with the NAS, 2x4GB wasn’t really an option and even with the 16GB it doesn’t flinch when PMS is transcoding.
What you’re seeing appears to work because of the SPD chip on the DIMMs and nothing more.
DSM (being Linux), reads the DIMM SPD chip. This tells it the size of the memory. It does simple math and reports what it finds. NOTHING MORE is happening. All of Linux can be spoofed this way.
If you want a test, Run memtest86+ on the box. Since it runs directly on the hardware, and sizes memory when it starts, you will get an accurate size.
Do you really think Intel would err in the amount of memory the CPU can use? Hardly.
As for 2x 4GB for transcoding, I have stated this many times elsewhere. This is dual channel mode being enabled by the CPU’s memory controller at POST.
I’ve currently got a Synology DS918+ running PMS with hardware transcoding on with the stock 4gb ram. I’m looking at upgrading the ram to 2x4gb sticks of the same type.
My question is, will running an Ubuntu VM on the NAS effect the performance of PMS and transcoding? You’ve stated in a few different posts that 8gb is the sweet spot for many users, just wondering how having 2gb allocated to VM will effect the performance / dual channel of the ram and if 6gb will be enough left over.
I know there isn’t a lot of other options here (as the 16gb thing seems false), however I could consider not running VM if it was going to be insufficient ram for plex to do it’s thing.
Running a Ubuntu VM on that NAS will kill it. You can’t do both (Plex and a heavy Ubuntu VM). There simply is not enough CPU power. You have 2131 passmarks. I have a 7 year old i7-mobile processor with 8300 passmarks which can run a VM but is still sluggish at times. You will find, running just Plex on the NAS, handling subtitles will be painful if it has to burn in image-based (PGS, or VOBSUB type). In most cases, subtitle burning will bring it properly “to its knees”.
Regarding the memory: Intel certified 8GB due to the SODIMMs available at the time. It should be able to do 16GB for you as 2x 8GB (“matched pair” is important here) in a 16GB “kit”. Again, folks do it and seem to be ok. Intel guarantees 8GB, Synology only guarantees 8GB. The rest is your decision. 8GB will give you plenty of room to run HW transcoding of the J3455 to its limit. You will run out of CPU ASIC (GPU) transcoding power before you run out of memory if you have 8GB installed.
Okay that’s very interesting to know, I figured the quad core processor on the 918+ would be fine to run an Ubuntu VM (especially with plex having hardware acceleration turned on). It’s all up and running, but the PMS hasn’t actually had to transcode yet AFAIK it’s only been direct play on the nvidia shield TV.
The only reason I would ever have to go over 8gb then would be the VM, but if I’ll be hitting a CPU limitation first then I might have to rethink my decision.
That’s a bit of a bummer, I really assumed this NAS was going to be powerful enough for both, the only reason I’m currently running ubuntu is for the PIA VPN app so I think it’s back to the drawing board for a better solution then.
Thanks for this information.
edit: I should mention I’m only really running two services on this VM and will basically never need to access the GUI, so maybe that will be okay? I haven’t noticed large CPU usage.
Well that’s too late now on the QNAP front, I guess the boasting about 2 x 4k streams
on the 918+ transcoding was all hardware accelerated.
Surely running Ubuntu VM without needing to access it shouldn’t use THAT much CPU. I think I might just go for the 16gb and be done with it then, maybe try allocating 4gb of ram to the VM.
I don’t think the plex server will have to work too hard until I start building a 4k library, most of my users direct play currently (video at least).
What I’m most disappointed with is hardware acceleration on my Synology DS918+. My family (remote users) and I like to have subtitles always enabled, but most of my movies are Blu Ray (PGS) subtitles which requires an additional impact on transcoding. When I enabled HW encoding, I get “Buffering” messages about every 10 seconds of play for a 10-second pause, wash-rinse-repeat. It’s so painful to attempt to watch a movie, that I turned it off in exasperation.
On the other hand, when I disabled HW Acceleration, the CPU hiked to about 90%, the play was smooth (for the most part), and I had no issues, until… one of my family members jumped in to watch a movie with subtitles. The “Buffering” returned and slowed the movie down so badly, that I stopped watching.
This is NOT a Plex problem, but a Synology problem. The answer seems to move from Synology to QNAP with a hefty processor (Intel i3, i5, or i7) with a built-in Intel video chip, plus the ability to add in a separate video card and offload transcoding to its built-in GPU. After researching the costs of QNAP, I almost wonder if I shouldn’t just purchase my own server!
At this time, I need to either upgrade all four drives from 8TB to 12TB ($1,400 investment) or 14TB ($1,700 investment) or purchase a much better chassis from a different vendor (QNAP?) and move the drives from the Synology to the new system.
I’ve had the same problems. That’s why i’m just using my Synology as a NAS and an old i5 laptop as a my Plex Server… Works way better than the NAS. I’m going to save up to build my own server.
