Plex Transcoding performance (initial measurements)

[Michael Wulff Nielsen]

Hi everybody,

excuse me if this is posted in the wrong forum, but I did some rudimentary performance testing using the FreeNas Plex service.

I was trying to figure out what would be required cpu wise to run the plex-jail and have adequate transcoding performance.

This was is my test-system:

FreeNAS-9.1.1-RELEASE-x64 (a752d35)
Intel(R) Core(TM)2 Duo CPU E4600 @ 2.40GHz
2000MB memory
250 GB Seagate SATA Disk (formatted to zfs)
1 GB Connection to my home network

Now I will point out that this is not a production FreeNAS system. It was never meant to be and it is most certainly not suited to be in production.

I tested the transcoding performance using an HD movie file with the following specs:

1920x1080p @ 12414 kps with an audiostream @ 1509 kpbs in an MKV container.

I had 4 clients available for the test:

1. Mac Mini (able to do it's own transcoding)
2. iPad
3. iPhone
4. Panasonic 50" VT60 Plasma TV (talks to plex via DLNA)

1. test: Mac Mini alone:
As expected even my test-system could stream the movie to the mini with no problems. Cpu load was negligible.

2. test: Mac mini + iPad:
This combination also worked fine. There was no stuttering at all in the video. The transcoding session did however take a little while to start. Both cpu-cores were active with top reporting about 166% cpu usage.

3. test: Mac mini + iPad + iPhone:
At this point I started to see some occasional stuttering on the Mac mini playback, I believe this was caused by the transcoding process simply used up all available cpu power.

4. test: Panasonic TV
Plex has to transcode the mkv to an mp4 stream that fits the tv. This is beyond what the small cpu in my test system can manage. The video plays until the buffer is empty and it then takes a few seconds to fill up buffer again. The image quality also degrades slightly because of the transcoding at high resolution. So I would not recommend this setup if you care at all about quality.

Conclusion
Without having 100% solid proof I would suspect that any modern cpu can do plex transcoding at an acceptable level. The two processors I considered for my personal nas build are the Core i3-4130 or the Xeon E3-1220 V3. After my very non-scientific test I am quite sure that I will choose the Core i3 as it is quite a bit cheaper where I live.

Be advised that if you choose the i3 you forego the encryption instructions that the Xeon has. So if you plan on using full disk encryption go for the Xeon. (Updated: The i3 has encryption instructions, thanks Dusan).


Your feedback is much appreciated.

/Michael

 

[Dusan]

The two processors I considered for my personal nas build are the Core i3-4130 or the Xeon E3-1220 V3. After my very non-scientific test I am quite sure that I will choose the Core i3 as it is quite a bit cheaper where I live.

Be advised that if you choose the i3 you forego the encryption instructions that the Xeon has. So if you plan on using full disk encryption go for the Xeon.

i3-4130 does support AES NI.

 

[Michael Wulff Nielsen]

Whoops, I missed that. But it just makes the argument for i3 even better. Thanks for the update. I will edit the post. :)

 

[scurrier]

Thanks for this valuable information. I just tested on my FreeNAS test box, running a Q6600. It can stream to my phone just fine via the chrome browser in android, streaming a pure bluray mkv. But it chokes pretty bad when I tried skipping around in the same video on my XBOX 360. I checked top and it appeared that one core was totally maxed out. I was surprised that it didn't utilize extra cores like Handbrake would for transcoding.

How is the i3-4130 doing, have you tested that? I have one sitting new in a box over here and wondering if I should ebay it or keep it for my FreeNAS. Transcoding is probably the use case that would cause me to upgrade.

 

[scurrier]

Found this post by you saying it works well for your ipad/iphone. Any elaboration would be welcome but I'm glad to hear that it works well in that case.

http://forums.freenas.org/index.php?threads/lower-power-versus-faster-processor.18144/#post-98668

I think my bluray rips are higher profile than yours, so if you have any input on that it would be appreciated.