Dual Xeons or single i3-6100?

Plex Media Server Desktops & Laptops
,
1

This may be a dumb question, but I am looking to redo my plex setup and expand my storage capacity from the mini htpc I’m currently running. Also, I need more transcoding capabilities, as a lot of shows I watch have subtitles which prevent direct play, and sometimes I need to serve more than 1 stream at a time.

I have two systems lying around. One is a Dell Poweredge R610 I saved from being junked recently. It’s got dual Xeon X5675’s, 4GB RAM per CPU, and six drive bay slots for 2.5" drives (SAS/SATA). The second is an old budget gaming rig, with an i3-6100, 4GB RAM, and room for two 3.5" drives and two 2.5" drives.

How does Plex handle multiple threads and multiple CPUs? I’m not really sure what’s best here for performance, the i3-6100 has much better single core performance than the xeon, but the xeon will run away if all 24 logical cores can be used between the two HT-enabled hexa-core CPUs.

I’m also aware of the generalization that you can transcode one 1080p stream for every 2000 points on a CPU’s passmark. Well, the Xeon X5675 scores an amazing 12k in a dual socket configuration, but the single threaded performance is only 1402, vs 2108 for the i3-6100. Does this matter in terms of transcoding, or will it scale to more cores all the time?

2

Plex has a lot of threading capabilities but some operations are single threaded (certain codecs and subtitles for one).

I need to advise you about your CPU performance: 8484 Passmarks
https://www.cpubenchmark.net/cpu.php?cpu=Intel+Xeon+X5675+%40+3.07GHz&id=1309

My i7-3740qm (2012 vintage) has 8332 passmarks and can handle 2x 20 Mbps software H.264 transcodes. It also has 16 GB of RAM. you’re going to need more RAM.

The i3-6100 5493 Passmarks
https://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i3-6100+%40+3.70GHz&id=2617

I advise revising your expectations. If the Xeon, with all 24 cores can only generate 8000 Passmarks, it might be time to consider other options.

3

Hi Chuck,

I have a dual socket system, so there are two Xeon 5675’s, not one: https://www.cpubenchmark.net/cpu.php?cpu=Intel+Xeon+X5675+%40+3.07GHz&id=1309&cpuCount=2

So 12 cores are getting 12k. The single CPU is getting 8k with six cores.

So that’s sort of my question, will Plex scale well with a dual socket system? What specific features are single-threaded? Is h.264 scalable, for example? Most of my content is h.264 encoded .mkv with multiple audio and subtitle tracks, typically 1080 at around 10-15mbps (variable bitrate).

4

If the OS sees it as one SMP (Symetric Multi Processor) configuration, you’ll have a CPU with a lot of cores.

Here’s where you’re going to get in trouble and why I suggested you reconsider your expectations.

If 12 cores are giving you 12,000 passmarks, that’s 1000 Passmarks / core (your numbers).

If you are only reading the files and decoding the file, at most converting the audio (some codecs will consume 1000 Passmarks with ease converting it), and remuxing H.264 to HLS (for something like a tablet), that will likely fit in two cores but it’s tight.

PMS will scale if it needs to transode, to a point. The codec does have a max threads it will use and that depends on each codec. H.264 will scale nicely up to about 4 (4000 passmarks), now let’s add the very heavy 7.1 audio -> Stereo conversion (another core) for 750, and let’s say 500 for the actual decode and remux operations of that H.264.

4000 passmarks gives us a 30 Mbps H.264 transcode (e.g. 1080p -> 720p of a tablet)
900 passmarks for the audio
500 for the decode and remux (to be safe)

5400 Passmarks (estimate) to convert 30 Mbps H.264 from 1080p -> 720p and convert 7.1 audio to stereo.

It looks bad yes. and if you started two playbacks at the same time, they’d stutter until the buffers fill in the players. They will reach steady state.

If there is subtitle (Image formats) to do, you’re dead in the water. No single thread speed is fast enough to get it done even with only one video

What’s your actual use case? You know that and only you can decide.

If your media is mostly DirectPlay / DirectStream (audio conversion only) ready? You’ll have a screaming machine.

The numbers I shared with you are based on my 4 core system with it’s 1/2 core (hyperthreading capability). Argument can be made that it’s almost 6 real cores so even this machine only outputs 1500 / core in practice. Crazy, isn’t ?

To summarize Single-threaded:

  1. VC-1 video codec decode. Encode will always be H.264
  2. Subtitles (PGS, VOBSUB, etc) are single threaded and death to realtime, unless burned-in (turning the video into DirectPlay/DirectStream.
  3. Heavy audio codecs, while not single-threaded might as well be. They are costly.

This help?

Edit: Not sure what happened with the formatting. I did not bold the math deliberately

5

Yes, that is very helpful, thank you! So my use case does involve subtitles and up to two concurrent streams. It sounds like either way I need to re-encode those to burn in the subtitles. That would help the issue significantly.

Also, I’m looking at very simple 196kb stereo aac audio on all of my source files, as they were compressed with Handbrake previously. Can I safely cut the 900 extra points on that estimated passmark score in half, or more? If I cut the 30mbps in half, can I cut the 4000 passmark score in half as well?

Assuming I can do both of those things and subtitles can be burned in, the new estimate would be lower. It sounds like I need to find a different processor that will be around the 2500-3000 range per simultaneous stream, or 6000 total for two concurrent streams. Perhaps upgrading the i3-6100 to an i5-6600 may do the job for my use case with some headroom for background tasks? That has a 7756 passmark and a 2095 single-thread rating.

Do I have this math right or am I making a mistake somewhere?

6

Some things which will help you:

  1. MP4 output (most compatible for DirectPlay of video stream
  2. Burn in the subtitles
  3. AAC audio (any bitrate) is fine. AC-3 also fine and trivial to convert if needed
  4. Keep the video at max bitrate is also fine. (why destroy quality if you don’t have to)

if you’re audio + DirectStream, that 12,000 passmarks will take you to SERIOUS bitrates of video and it won’t break a sweat :slight_smile:

7

I get where you’re coming from here but storage is also an issue. I’ve got about 200 blurays to rip and that’s an insane amount of storage to keep, particularly when talking about burning in subtitles and using max bitrate. Then add in the fact that a good chunk are anime blurays with dual english/japanese audio/subtitles and english audio/subtitles that don’t match up, it would mean keeping two copies of those in order to have burned in subtitles. As much as I’d like to just grab a few 10TB drives, it’s just too expensive especially when accounting for a second set of drives as backup. That’s why I’m using hardware I have lying around in the first place, you know? My library needs to fit into 5TB, hence the compression.

I did happen to come across an i5-7600 for $160 though, so I’ve installed that in the 6100 tower (motherboard was compatible with a bios upgrade), so I think now I should have no problems with transcoding for 1-2 streams based on your experience with the i7-3740qm (similar passmark scores). I will use the R610 for web/program development and as an extra handbrake system to handle the library compression. If I compress using something like a 18 constant quality setting on handbrake and slow encoder preset, I should get near a 4:1-7:1 compression without really losing anything in terms of quality. I’ve done a lot of screenshot and video comparisons to confirm this, the pictures wind up being almost identical.

8

Be also advised, The KabyLake (-7xxx) CPUs are capable of HEVC decode where the SkyLake (-6xxx) and below are not.

9

All of my videos are h.264. Wouldn’t quick sync have worked with either in that case since h.264 was supported all the way back to Sandy Bridge? Does that also mean the passmark scores are less relevant?

10

Just because a Sandy Bridge is ‘technically capable’ doesn’t mean it’s the most sophisticated silicon and does a great job or can handle high bitrate.

Speaking to bitrate, you referenced the 3000 Passmark number. If I may reiterate for clarity,

2000 Passmarks / 10 Mbps video / stream of H.264. e.g. A single 20 Mbps video needs around 4000.
3000 Passmarks / 10 Mbps video / stream of H.265. e.g. A single 20 Mbps video needs around 6000.

11

I see. It’s kind of difficult to follow, the doc pages don’t really say much beyond a “minimum” requirement, and saying that Haswell and newer are “better”

I do appreciate the time and help, thanks a lot!

12

You’re very welcome.

This level of detail is tough to fit into the support doc page and keep updated.
That’s why I decided to share what everyone is seeing in real-world use cases.

13

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.