PIER78: December 2013

Chromebook (C7) as a Media Server

4:38 PMPier78

I decided to update this post and streamline it bit since I felt users who just wanted to set up a C7 as a Plex Media Server probably wouldn't want to sift through all the original wall of text. 1/24/2015

Using the C7 as a Plex Media Server
First off, you need to have crouton installed on your Chromebook. There are many guides on this such as this one: Crouton

Here's a run through:

If you don't have Crouton on your Chromebook (Skip Otherwise)

First off you need to be Developer mode for your Chromebook

This can be achieved by hitting esc + refresh + power button on your chromebook. note: switching to developer mode will wipe your data so do not do this until you have backed up anything you want to save
Your chromebook should reinstall and reboot
When it comes back up you will need to hit ctrl + d to load quickly into ChromeOS. note: you will always have to do this from now on when turning on the chromebook from a cold boot (other wise it takes long to get into ChromeOS and it will make a beeping noise). There is a work around this issue but from what I've read it is somewhat dangerous so I will not post how to do it here
Once developer mode is enabled

download crouton from: https://goo.gl/fd3zc
hit alt + ctrl + t. this opens a crosh tab which should look like a terminal
type shell and hit enter
type sh ~/Downloads/crouton -t cli-extra and hit enter. this should create a cli chroot environment without X
after it is done installing you should be able to enter your chroot environment using sudo enter-chroot command

Installing / Setting Up Plex

Personally I rather use my desktop to configure the chromebook so I would install SSH sudo apt-get install openssh-server

run ssh server: sudo /etc/init.d/ssh start
not sure if it applies to everyone else but I've had issues making connections to my chromebook if I do not flush iptables so I always have to run this script prior to using openssh/plex

The site shows the required commands such as the chmod for permission to run the script and the command for running the script: /root/fw.stop
Keep in mind you usually have to run this script prior to starting any of the servers (openssh or plex)

Then I would use PuTTy to tunnel in
I would also install the vim package since I haven't been able to kill my bad arrow key habits sudo apt-get install vim

Next I want to install Plex, the way I do it is downloading the deb file and just installing it manually

first install the dependencies

sudo apt-get install avahi-daemon avahi-utils

download plex

wget DOWNLOAD_URL
e.g "wget https://downloads.plex.tv/plex-media-server/0.9.11.7.803-87d0708/plexmediaserver_0.9.11.7.803-87d0708_amd64.deb"
FYI you can copy pasta with a chromebook in the terminal by using two finger tap on the pad to paste

install plex

sudo dpkg -i DEB_PACKAGE
e.g. "sudo dpkg -i plexmediaserver_0.9.11.7.803-87d0708_amd64.deb"
make sure you are in the right directory

start up plex

sudo /usr/sbin/start_pms plex

in my experience services seem to have issues on a chroot environment so I have to run plex using commands instead of the traditional "sudo service some_service_here start" command.

configure and use plex hooray

navigate on your browser localhost:32400/web/ [IF YOU ARE ON CHROMEBOOK]
navigate on your browser IP_ADDRESS_OF_CHROMEBOOK:32400/web/ [IF YOU ARE ON ANOTHER COMPUTER]

C7 as a Plex Server Performance Concerns
Using WinSCP and BitviseSSH, I have benchmarked file transfer speeds on the chromebook and it appears to be capped at about 16MB/s (using gigabit switch). Using htop, during file transfers the processor usage was capped out, as a result it appears to be a processor bottle neck rather than my initial impression that the hard drive was a bottleneck. the Intel Dual Core B847 1.1 GHz is a bit lackluster for a Plex Media Server, but works fine for directplay (no transcoding).

For a benchmark comparison, I had purchased for bit a under $80 on ebay recently, a Lenovo ThinkCentre with a E8400 Intel Core2 Duo and 3GB. I also had an old low-end rig with an Intel G620 for about $200 from about 2-3 years back. Processing Benchmarks. As a result the C7 is not a cost effective plex media server.

The C7 Experience
Based on my experiences, if you plan on using subtitles with the C7 as a Plex Media Server using the web player, it only has enough processing power for 720p quality with minimal stuttering during playback for one device and quite a bit of lag when skipping ahead or backtracking. Heavy stuttering occurs when viewing 1080p video with subtitles (the web player and android application requires the media server to render subtitles on top of each frame). However the PLEX HOME THEATRE Application (not the server) for Windows, Linux, Mac can utilize direct play with subtitles thus in this case, content does not stutter from the Chromebook.

Old Post:

So I'm not sure why but it seems that every program I install onto my chroot environment on the Chromebook doesn't seem to be able to install its corresponding service properly. As a result I pretty much cannot run any Media Server type of software:

sudo service some_service_here start
start: unknown job: some_service_here

Usually this results from broken installations but all of these programs were installed without a hitch using apt-get and reinstalling made no difference. Perhaps there is a configuration problem with my chroot environment.

Never the less when first installing Plex Media Server: Possible through apt-get or by getting the deb file from the Plex Website:

sudo apt-get install plexmediaserver

no issues occured aside from the fact I couldn't start it using service start commands--instead I used:

sudo /usr/sbin/start_pms plex

Then I headed over to (using a browser) localhost:32400/web/ to configure the location of the library and other options. Then when I tried to stream something...I got nothing. The web browser player displayed a loading animation so I thought the Chromebook didn't have enough grunt for transcoding. However I used htop to check cpu usage (I scrapped xfce and x altogether and just run the chroot environment through command line) and noticed the usage was sitting ~2-5% per core. My C7 has a 1.1GHz Sandy Bridge Dual Core Celeron processor. So this pointed out that the processor wasn't even transcoding at this point, something else was up. I terminated the server (ctrl + c) but for some reason other background processes were still running for Plex despite terminating the original process I executed so I had to terminate them individually.

Overall PLEX worked wonders on my Windows Server so I decided to have another go at it. This time I found the solution. Prior to installing PLEX using the deb file on their website, I needed to install two things:

sudo apt-get install avahi-daemon avahi-utils

Strangely enough when originally installing PLEX, it did not complain about not having these two dependencies installed. Second time around, it did complain. Still, I could not run PLEX through the service starting commands so I used the command from earlier to start PLEX. This time however, it streamed without a hitch, the CPU usage capped around ~5% per core while streaming the maximum web browser player settings (20Mbps for 1080p).

Not sure if its placebo or not, but it seemed to me that despite using the highest quality possible, there appeared to be noticeable quality loss in comparison with the Windows Server so I may need to look into this. Nevertheless it is working and I am happy with it.

So currently the Chromebook is on a crosh tab active on the 'precise' chroot environment running htop (I plan to have it on this 24/7 until I find a better informational utility to run). I control it with my main computer by using PuTTY and XMING to connect to the OpenSSH server installed on the Chromebook. In order to keep programs running using SSH, I started using a nifty program called screen.

sudo apt-get install screen

Closing PuTTY after executing a program will terminate that program so with screen I first create a session, for example: screen -S plex. It will create a new session where I can run a program and close PuTTY while keeping the application is still running. So I run PLEX then hit ctrl + a + d. This exits the screen, but the program running in the screen is still active. To go back to the screen I would use: screen -r plex. Then to close the screen I would terminate whatever program is running in the screen (if there is any) and just type exit.

For my current Chromebook Media Server configuration, I'd first turn off power saving since the Chromebook will automatically go to sleep when closing the lid. Then I would enter my chroot envrionment (thanks Crouton), then start up whatever servers I desire (for me, just OpenSSH and PLEX for now).

Edit: So I realized that I had directplay settings enabled meaning the server could simply avoid transcoding altogether and directly stream data to the browser for playing media. As a result after disabling direct play to test the transcoding abilities of the C7, it definitely does NOT have enough processing power to transcode 1080p at 20mbps. The C7 was capped 100% for both cores and there was heavy stuttering (unwatchable). For my case, this is fine as I am able to watch movies just fine on any computer or even on my android phone using DirectPlay.

Subtitles on the other hand, requires transcoding for PLEX. The cores max out ~99% each when using subtitles however, it is watchable (little to no stutter) but there are issues if you plan to skip around.

Edit #2: After watching more films that needed subtitles with, I figured that the Chromebook (C7) does not have enough processing power for subtitles at 1080p (my previous test was streaming a 720p documentary with subtitles). When using Plex Media Server, even with directplay enabled, subtitles are manually rendered onto each frame rather than being sent separately in an independent data stream. As a result using subtitles requires quite a bit of processing power from the server. However if you use the Desktop client for Plex to watch your movies, the application is able to acquire subtitle data separate from the media data stream (thus does not require transcoding in this case), the browser player is unable to do this.

Edit #3: The Android application for PLEX also does not support a separate data stream for subtitles independent of the video and audio stream. As a result the PLEX Android App will also require Transcoding (if using subtitles and/or directplay is disabled). Hopefully PLEX addresses this in the future.

black screen lucidlogix mvp

XBMC Black Screen Bug caused by LucidLogix Virtu MVP

10:06 PMPier78

So I was trying to get XBMC working and it appeared to get a black screen despite being a fresh install. A quick Google search showed that very few people had the same issue I had. Their cases were quite different as theirs revolved around unsupported hardware which was not my case. I tried re-downloading the installer in case of a corrupted download, searched for any old registry key residue, and did fresh reinstalls with different configurations to no avail.

Then I remembered I had LucidLogix Virtu MVP installed. This software comes with most non-budget motherboards. On the contrary, it came with my budget ASRock z77 Pro3 motherboard. The purpose of Virtu MVP is to intercept API calls and chooses which discrete Graphics Processor to pass these calls to. It takes advantage of the fact that despite most people using a dedicated Graphics Card, most Sandy Bridge and Ivy Bridge processors (aswell as the new Haswell processors) have a built in Graphics Processor on the CPU die. On the other hand this software is looked down upon in the benchmarking community since the software causes benchmarking tools to count frames that may not even be completely rendered--as a result measuring an inflated framerate count (subsequently inflated score).

Oh my did someone say more FPS???

LucidLogix Virtu MVP claims to:

Improve Game Responsiveness up to 70%
Increase V-Sync maximum frame rate from 60 to 120
Sharpen Visual quality without tearing

For the most part the software has brought me nothing but headaches causing issues ranging from increased load times for software that utilize the discrete graphics processor (in my case a GTX 670), software not functioning properly (such as XBMC here), strange graphical glitches, and contains memory leaks (?)--recently I disabled MVP and noticed once or twice that its daemon memory usage accumulated to about ~650 megabytes...while it wasn't being used!

The software re-enables itself after restart so after disabling the software, lo-and-behold! XBMC works perfectly. Seriously I think motherboard manufacturers should just drop this LucidLogix stuff until they show some serious results and benefits.

*Edit: I will admit however that I do like LucidLogix Virtu MVP's virtual V-sync that prevents tearing. It definitely worked when I was playing Civilization V.

acer c7 connect local network

Taking Forever to Fix a Small Problem

3:28 AMPier78

So today I decided to use my Chromebook as a server (again). Originally I was thinking about getting hobby boards like the Raspberry Pi, Cubieboard, Beaglebone Black..etc and after I had finished having fun with them I would use them as simple small Linux servers since they are fully capable of running full blown operating systems. I had a made of list of things I wanted to use them to host:

WordPress / MySQL / PHP
Mumble Server (Kind of like a Vent Server)
PLEX Server (Plex is awesome, maybe I should make a post about this)
File Server

However I was just eyeballing the cost of the boards, and server wise while they would be cool and quiet (fanless), and compact, they wouldn't make cost effective servers. The Raspberry (B) is at a reasonable $35. Although its processor seems under powered in comparison to the Cubie and Beagle, apparently its graphics processor packs a punch and hobbyist have been using it to watch 1080p content. Cubieboard seems great but it lacks documentation and seems somewhat hard to acquire in addition to its $80 price tag. The Beagleboard appears to be unable (surprisingly) to play 1080p content at 30/60 frames per second. Ultimately if I were to use these boards as servers they would probably only be able to support one server per board so I would have to add up the costs of many boards, then the cost of components per board.

There's just something about miniature computers like this that I find fascinating.

MicroSD storage ($~7 for 8gb)

The Cubieboard is awesome in the sense that it supports Harddrives as it has a SATA port. It also has a built-in 4GB NAND memory. Surprisingly some people thought of the NAND memory as a con as it uses board estate but personally I felt the board was substantially larger than the Beagle or Raspberri so if it was going to be that big it might as well loaded it with as much bells and whistles as possible.

Power Supply (~$7-10)
Plastic Cases ($~5-10)

I was actually thinking about using the extra space inside my ATX computer case since it has a lot of free room, but dealing with the ethernet cables and power sources would be quite troublesome. So cost wise it seemed to be more efficient to just buy used a Xeon off Ebay and build an actual server from used parts which could probably destroy these all these SoCs combined in performance. The PLEX Media Server in particular will be doing a lot of transcoding which many users claimed these boards (powered by ARM processors) simply don't have enough grunt to do. More or less the Raspberry Pi seems like a cost effective tiny tiny computer with some pin outs. Perhaps I will look at these kind of boards again another time as they certainly seem fun to play with.

So as a result I decided instead of splurging on those boards I would try to use the Chromebook as a server since it is collecting dust anyways (unfortunately). So currently I have used Crouton to run an Xubuntu environment. I believe it is currently only on 12.04 as I haven't had much time to dabble with updates.

Currently my plan is to install:

Synergy (Share KB + Mouse, crossplatform since my desktop is on Windows 8.1)
OpenSSH
Mumble Server
Plex Server

Synergy is currently installed, unfortunately the server software doesn't seem to be compatible with my Desktop on Windows 8.1 (appears to only support up to Windows 7) so I will be attempting to look for a solution for that. OpenSSH has been installed but despite a simple installation too me FOREVER to fix an issue (will continue on about it in a moment). I currently have not installed the Mumble Server yet as I will have to confirm with my friends whether they are willing to make the switch to the software as an alternative to Skype. The Plex Server software has been installed by has not been setup yet.

Unable to connect to OpenSSH on a local network

Anyways the big problem I had just moments ago was that despite being able to connect via SSH locally, for some strange reason using PuTTY to access my Chromebook from my Desktop kept timing out. I double checked configurations, double checked the firewall setup with UFW for port configurations but it still didn't work. I was stumped and searched for hours on the Internet for a solution. Then it hit me--I never flushed IPTables after installing UFW. After flushing IPTables and restarting SSHD (SSH Daemon) I was able to access my Chromebook via SSH. I felt like smashing my face onto my keyboard. 4 hours for such a simple solution.

I fixed the issue with Synergy. I had a custom configuration for my system variables on Windows 8 to store temporary files on my D: drive since my solid state hard drive C: is tight on space. The temporary folder had a space between it (it was called Temp Files). Simply changing the system variables to TempFiles and renaming the actual folder fixed the issue.

amd amd crossfire ati

Dual GPU Dilemma

3:26 AMPier78

The Dilemma
Generally speaking, every post I've read (whether its on [H]ardforums, TomsHardware, Anandtech, TechSpot etc etc...) asking about whether they should go the Single GPU route or Dual GPU route is always bombarded with posts recommending the Single GPU route citing issues with Dual GPU setups and what not. Although I would say that is the case in most situations, I personally feel that OP's of these threads should really tell more about their situation as I have personally experienced both CF/SLI and feel that the choice needs to be determined by a case by case basis.

Background
So first off I've lived with 6850 Crossfire for about 2 years, but have recently switched to a single GTX 670 and have been staying with that for a couple of months. Prior to this I've also run 4850x2's in Crossfire and 9800GT's in SLI. However during the 4xxx ATI and 9xxx Nvidia days, I can safely say that it was not worth the cost--but times have changed, the technology has improved and I feel that it is a true contender for frames per dollar. Unfortunately I started this blog after I switched to the GTX 670 so I didn't take any screenshots to show hard proof to backup what I say, but there's more than enough reviews and benchmarks from the plethora of Tech Review Sites that currently exist to give you a better idea of the multi-GPU Technology.

Content
First I'm going to start off with the issue's I've experienced with Crossfire (most of this stuff applies to SLI aswell but SLI DOES differ from Crossfire in some aspects for better or worse). Then I'll cover what benefits of Crossfire I've experienced and then conclude with a sort of a case by case basis on whether multi-GPUs are for you or not.

Intricacies of Crossfire / Multi GPU

Not all games support Multi GPU setups

This is probably the biggest issue of Multi-GPU setup's and the most common reason people do not recommend CF/SLI. Isn't it wasteful to spend money on something that only works most of the time?
In some cases, you actually get WORSE performance for applications that cause negative CF/SLI scaling.

Graphical Glitches in games

The only game that produced this issue for me was The Secret World using the Dreamworld Engine produced by FUNCOM.

The Game had serious flickering issues with shadow and lighting, and text appeared corrupted and unreadable. Both these issues occurred only in DX11 mode. DX9 did not have the issues but Crossfire scaling was nowhere as good as in DX11 mode.

Greater reliance on drivers

Multi-GPU setups are seriously reliant on AMD/Nvidia to chug out profiles and modifications to their drivers to utilize the GPU's. This propagates an issue with BRAND CHOICE.

NVIDIA for the most part seems to have a better track record with pushing out drivers (as well as SLI Profiles). During my 6850 days I would wait months for a driver update from AMD while NVIDIA usually provides an update every month or so.
The most recent issue I dealt with was when I was tried out Final Fantasy XIV in beta. SLI was ready a month or two prior to Crossfire supporting the game.

Requires an SLI/CF Compatible Board

This is one of the reasons multi-GPU setups need to be looked at on a case by case basis. If a person is planning to purchase a motherboard that supports it or already has a mobo that already supports it, this is not really a con.

Most mid-ranged/sub-enthusiast boards have multiple PCI-E 2.0/3.0 slots that support atleast x8/x8 (~$100+ mobos)

Generally people get these boards for more power phases for better OCing capabilities and more general features on their motherboards.

Note: I read a thread on the EVGA forums with benchmarks showing PCI-E 2.0 as a bottleneck for ultra-high resolution gaming. As a result motherboards with multiple PCI-E 3.0 slots is something to look at if you plan to do this. Then again if you have many expensives monitors, you probably already have an high-end enthusiast mobo already which does have multiple PCI-E 3.0 slots ($200+ motherboards)

Greater Power Consumption

More processing power -> More power consumption.
I think this issue goes either way. For example in my case, 6850's in crossfire actually use less power on load than a single GTX 480. However you could just say that would be an embarrassment on NVIDIA's end with their Fermi architecture.

Greater Heat Production

Again another obvious point, but depends if the extra performance is worth the extra heat to the user.

Primary GPU Runs hotter by ~10C

This can be caused by multiple things:

From Guru3D

From Hardware.info

The two Cards are too close together which results in less air flow to one of the GPUs since the PCB of the second card inhibits the air from entering the intake of the first card.

This usually only applies to motherboards that put PCI-E slots too close together
Most MicroATX motherboards have only have a single PCI-E x1 slot in between each x16 slot to fit the smaller form factor, somewhat unavoidable for smaller rigs.
You can try cramming a small piece of styrofoam reduce the impedance of air flow--this mitigated the issue for my friend so even a couple millimeters helps

In Crossfire (not sure if this applies to SLI), memory clock for the primary GPU is ALWAYS on load IF YOU ARE USING MULTIPLE MONITORS. If I recall correctly, this was design by AMD to prevent a flickering issue from memory frequency to low to drive both monitors. This also results in increased temperatures on the primary GPU

I got around this issue by forcing lower clocks with MSI Afterburner with unofficial overclocking settings for idle/2D mode.
Update 10/19/2014: This was fixed in more recent catalyst drivers (I think)

Update: I added a dedicated Physx Card in conjunction to my GTX 670 (I got a cheapo GTX 465 for about $40 off ebay). Despite the fact that the cards are not in SLI, and are also well spaced apart, the GTX 670 runs about 10C hotter on load with the 465 in the case! I did not anticipate simply having the extra card would cause such a significant increase in Load temperatures. Of course this also maybe just because the dedicated (465) Physx card is Fermi architecture video card. Fermi runs too hot, and uses too much power for the performance it provides. (It is a Galaxy GTX 465 with a 'flip fan' design.)

Video RAM does NOT Stack in SLI/CF

A common misconception is that if I have one Video Card with 1 GB, if I get another one and put them in SLI or CF, I will have 2 GB! No! This is incorrect unfortunately.
This issue even applies to sandwich cards (dual GPU, one PCB): ARES, x2's, MARS, GTX 690/590, AMD 7990/6990 etc or those special cards (dual GPU, two PCB using with one PCI-E bus) GTX 295, Geforce 7950 GX2.
Think of it like this: Pretend Video Games are like moving stuff from your old house to a new house. You have a choice of DUAL GPU--Two Toyota Corollas, or a single GPU equivalent--Ford F150 Pickup Truck. We'll say that video memory (lets call it VRAM) is the capacity to hold things in each car. So the corolla has a small trunk but has seats that can hold stuff. So let's say that each corolla is equivalent to 1 gigabyte of VRAM, and technically since I have two corollas, I can bring twice as many things in one go--I have technically 2GB. The Ford pickup truck is well..a pick up truck and has LOTS of carrying space, so lets say that the Ford on its own has 2GB of VRAM.

For the most part if I only need carrying many small objects, these two Corollas maybe be able to carry just as much things as the F150. In this case the games don't use much VRAM and as a result these dual GPU's can perform just as good if not better than the single F150.
But what if the game needs MORE than 1GB of VRAM? What if the object I am trying to move is large, like a refrigerator? The F150 will have no issue carrying this. The two corollas on the other hand..well..tough luck. Technically they have 2GB but since these cars are physically independent of each other, they don't combine individual capacity into a singular usable net capacity.
In the same manner, the two graphics card in a Dual GPU setup are physically independent of each other. Each card can only use its own 1GB (or whatever amount of memory it has) to produce a frame. Then these two GPU's combine their frames together to produce an overall net increase in frame production.

Some video cards of same generation/model but different edition may have variations in VRAM capacity. When running in SLI/CF, if you have mismatched VRAM, the smaller capacity is used. A general rule of thumb in computing: you are only as fast as your weakest link.

This also applies to HYBRID Crossfire, the faster card will slow down to match the performance of the slower card.

Windowed Mode disables CF (and sometimes SLI)

If you do not play games on fullscreen, multi-GPU setups will be problematic. This includes borderless windowed mode--yes that's right you alt-tabbers.

CF Simply does not work in non-fullscreen, and I have confirmed through GPU-Z. Even If I force 3D clocks using Afterburner, during windowed mode or borderless windowed mode the second GPU will be at 0% utilization.
I do not know the technicalities of why this occurs, hopefully I find something about it and will add it here.

Some people claim SLI sometimes works/sometimes doesn't with Windowed Mode. I never checked this when I was running 9800GT's and those are long gone, plus SLI has changed so I can't confirm with a modern pair of cards (perhaps if I SLI 670's? c:)

Microstutter

Microstutter is a visual stuttering effect caused by variations in the time it takes to render each frame, despite apparent constant high framerate.

Frame rate is not measured at Hardware (GPU) Render Time

Is Microstutter real? Yup. Some people on forums claim its placebo but it's real as I have experienced first hand. However, sometimes it is more difficult to see. For example one of the demonstrations I was shown was in the video game Sleeping Dogs. In that video, which was slowed down, it was blatantly obvious that there was stutter--BUT, prior to seeing this video I had I played through the entire game on my 6850's CF @ 1080p maxed settings and didn't notice any stutter at all. My first experience with microstutter was actually in Far Cry 3. When running through the jungles with lush flora, it was very clear that my game was stuttering despite a purported 60+FPS measured by Afterburner.
This also propagates an issue with BRAND Choice.

NVIDIA's SLI was claimed to produce 5% frame variation in a single GPU setup vs 7% frame variation in a DUAL GPU setup (GTX 680s).
AMD's 7970 single GPU test had a variation of 7% compared to a staggering 85% frame variation in Crossfire X.

Source: SWEClockers Article (in Swedish)

"AMD could meet (and beat) NVIDIA on frame rates, only to lose out on smoothness as a result of poor frame pacing," Ryan Smith from AnandTech.
On the other hand, AMD has recently released a Frame Pacing driver to reduce this stutter. This is a software solution that looks at variation in frame time and introduces artificial delays to smooth out this variation. Of course this results in overhead, roughly 5% performance loss: HardOCP Article

However it has issues with with EYEFINITY and 4K Resolutions
Source: Techreport 13.9 Article

IIRC, NVIDIA uses a hardware solution for frame pacing, as a result has has a more consistent frame interval without the same kind of overhead.
Generally Crossfire scales better than SLI but is not as smooth from frame variation.

Problematic with Video Capture

With Software like OpenBroadcaster, FRAPS, DXTORY, X-Split, multi-gpu setup is problematic. However you can bypass this problem with capture cards--use a secondary computer to capture video output and record/stream from that computer.
Software like OpenBroadcaster pull the frames directly from the primary GPU and does not grab frames from the video output. As a result despite having multiple-gpus producing frames to create a unified smooth experience, the software only pulls the frames produced on the primary GPU. As a result, despite a purported high frame rate, the actual recording/stream will appear as if it is stuttering if you rely on both GPU's to produce a unified smooth experience (ie: If both GPU's work together to produce 40 fps, the recording will only be about 20 fps produced by the primary GPU).

OBS Support for CF/SLI in the future, not looking good.
From my own experience, however, OBS wasn't "pulling frames" off the primary GPU. Instead, Crossfire would work right until the point I hit "Start Recording,"--then the GPU#2 utilization percentage would drop to 0. The game I tested this with was Hitman Absolution. The OBSProject forums has numerous threads like this describing the issue.
Some people claim this issue is GAME DEPENDENT but I feel that since the issue revolves around the the design of SLI/CF, then it should be an issue that persists regardless of the application.

I think the people who claim that OBS works fine with SLI/CF probably aren't even checking if the second GPU utilization greater than 0% while recording
Or rather don't notice a framerate drop significant enough to warrant a check with CF/SLI being disabled (as they have very high end cards, or recording a non graphic intensive game-- card is able to maintain fluid frame rate with one card [30-45+ FPS])
They maybe even attributing the framerate drop as nature of recording software (framerate drops are normal when recording but the amount I was experiencing virtually made the game unplayable)
Despite streaming numerous times before, I didn't even notice this issue until the last few months that of using 6850's in Crossfire--I attempted to stream Hitman Absolution at near max settings 1080p, when the game would choke horribly while recording, but play very smoothly when OBS was not recording). The game was running at 1080p but OBS was recording at 720p.
Off topic: I am by no means a big streamer, but I stream privately to my small group of friends to share with them what I am doing. At times we even stream ourselves doing work or studying/homework! Basically its screen-sharing without Skype or Google Hangouts.

Personally when testing Video Capture with Crossfire X, DXTORY is the only application that supported multiple GPU video capture but it was seriously buggy and unstable (crashes, freezing etc.) OpenBroadcaster--Crossfire works right until you press that record button, then you can see the second GPU will drop to 0% utilization.

Overclocking limited by weakest link

While overclocking is possible with a multi-GPU setup, you are limited by the card that overclocks the worst. This is due to the nature of Crossfire/SLI which syncs the cards to perform at the speed of the slower card.

Higher Cost to Upgrade, Dead End Upgrading

For those who stuck to the single GPU route, they now have the capacity to tack on a second GPU to improve performance. If you used 2 or more GPU's for your current setup but you still want more, looks like you will need to scrap them all.

More Noise

More fans -> More noise

Pros of Multi-GPU

Greater Price to Performance Ratio

Although the negative intricacies of Crossfire/SLI may seem to stack heavily against the number of benefits, the VALUE of a product should always have the highest priority making deciding on a purchase.
Crossfire/SLI provides a really solid value for its cost:

For games that do support multi-gpu configurations, 6850's in Crossfire perform just as well as GTX 580's
Retail cost of a GTX 580 is $400+, retail values of of each 6850 was about $150. That's nearly $100 less for similar performance.

In actual cost, I purchased my 6850's brand new for ~100 each when they were nearing EOL.
6850 Crossfire Benchmarks
More 6850 Crossfire Benchmarks

As can be seen in the benchmarks, adding a second card in crossfire effectively doubled the frame rate.

Greater Performance Capabilities

For those looking for just raw performance, building the fastest of the fast gaming computer at any cost, you will need to go the route of multi-GPU.
KingPin sitting at the top of 3DMark with 4xTitans

Better Crypto Currency Mining

I don't know much about this as I personally have never mined Bitcoin, LiteCoin or even DogeCoin, but most mining setup's I've seen use multiple GPU's running underclocked since it you want to have a net gain from mining after considering the cost of electricity. Multiple underclocked GPUs appear to provide better efficiency over a faster single GPU setup.
Personally this is not a benefit for me but it maybe to others.
This propagates an Issue with BRAND CHOICE:

AMD cards are more efficient and overall better at mining crypto currency. I've read somewhere claiming that the reason for this is due to AMD's GPU architecture--it supports a bit shifting instruction which (due to the nature of cryptocurrency) increases efficiency of mining by a substantial amount (this instruction has little benefit to games). As a result, AMD's card prices are currently inflated (1/7/2014).

E-Peen (Internet Ego) Boosting

Two is better than one and I have two! Haha! I'm better than you cause I have more!
"More is better"

Doing a Case by Case Look:

TL;DR: Use this beautiful chart I made (Just kidding it needs work)
Open the image in a new browser tab as it is too large for the image viewer on blogger...

Reasoning behind the Chart:

My current Mobo choice doesn't support CF/SLI!

If want to upgrade and your current motherboard doesn't support SLI/CF then you should stick with the single GPU route unless there are some goodies in addition to just CF/SLI for getting a more expensive board. If you are happy with what you have, why spend MUCH more (cost of mobo + cost of GPU set) just to try out something you may not even fully appreciate?

Is it worth it if I change my mobo (to support SLI/CF) ?

It's really up to you if you want to spend a bit more. Personally I feel that most people get higher end boards for more reasons that just SLI/CF. More expensive boards provide capabilities like more extra power phases for CPU OCing, greater number of 6Gbps SATA ports, better onboard audio, onboard SATA controller, higher memory clock frequency support and of course E-peen.

Keep in mind though, higher end boards do have greater power consumption (10-20watts). This is generally nothing to most computer builders but IS reduced inefficiency nevertheless. If every watt matters (you are paying for electricity, tight on money...take a step back for a moment)

Motherboard Power Consumption Variation

My power supply is inadequate or less than 650Watts!

I actually used a 600 watt Power Supply for my 6850's in crossfire--and this was in conjunction with an ASUS P67PRO motherboard, Core I5 Intel 2500K, four hard drives, 4 x 4GB Patriot Viper 3 Series RAM sticks, and 8 case fans. Check the wattage of the cards you want to SLI/CF. If you are looking for a low wattage rig with less than 600 watts, you should probably avoid the multi-GPU route. If you need to spend more on a higher wattage power supply in addition to the costs of the GPU's, you may want to take another step back.

Consider the multi-GPU route: There are two good routes for dual GPU setups, Mid-High Multi-GPU or Flagship/Enthusiast Multi-GPU. Do not bother with SLI/CF if you are planning to use low end GPUs, the value is nowhere near the mid-high+ range multi-gpu setups. Back in high school I had a friend who rocked 9400GT's in SLI....9400GTs in SLI produce half the frame rate of a SINGLE 9800GT (9800GT's were ~$100ish compared to 9400GTs ~$40-50 each).

The reason I also feel Mid-High Multi-GPU's are a sweet spot because not only are they good for the price to performance ratio, but when you play a game that doesn't support CF/SLI, since the single card is already a mid-high ranged card, so it doesn't sting as bad when it doesn't work (MID-HIGH Ranged cards refer to cards ~$250 or above in costs, such as the GTX 760)--while the GTX 760 is no where as fast or expensive as the GTX 780TI ($700?), it can definitely play most modern games at 1080p at max or near maxed settings at about ~60 frames per second. So say if you put two GTX 760's in SLI, even though if you play a game doesn't support SLI, you'd still have an reasonably enjoyable experience.

Type of Gamer/User is IMPORTANT

As I have pointed out early, there are a lot of intricacies with using Crossfire/Multi-GPU setups. For Multi-GPU's, the individual needs be someone willingly to work with their computer and understand it may take a bit of effort and tweaking to get the best performance. If you just want to buy a card, install drivers and expect the best performance you can get with that card instantly, don't bother with Multi-GPU.

The Gamers:

The person who is a 'hardcore gamer' or potential 'pro gamer' that plays that one game and that one game ONLY.
Well then does that one game support Crossfire/SLI?

The person play triple A game titles, hasn't touched an indie game before.
Well then lucky you, most big name game studios use big name game engines like Unreal, EPIC, Unity, Source Engine, for their games--and of course they support multi-gpu configurations out of the box. As a result you can pretty much guarantee triple A titles will support Crossfire/SLI (but don't hold your breath, some dev studios just want to watch the world burn). Blizzard is one of the exceptions as I've always had negative scaling with Blizzard games on multi-GPU setups. However more recent benchmarks it seems like World of Warcraft likes SLI (but not Crossfire), Starcraft benefit very little from multi-gpu setups. Nevertheless even most in-house engines by big developers like Frostbite by DICE support multi-gpu setups so overall if you play primarily big studio games, it is pretty safe to assume that SLI/CF will work.

The person who plays mostly Indie or Small Developer/Free to Play type games.
I do not recommend going Multi-GPU for this case. Most indie games such as MINECRAFT do not support Multi-GPU configurations and probably never will. There are some exceptions, for example the indie developers that created Shadowrun Returns (Harebrained Schemes), used Unity Engine. The game, despite being developed by an Indie studio supported Crossfire since the engine supports multi-gpu setups out of the box.

The well rounded gamer; the one that does not discriminate and plays them all like Pokemon.
Some will work, some will not work (obviously) which is why I recommend mid-high or flagship GPU setups so the games that don't support multi-GPU setups still play well (just probably not at maxed settings).

The gamer but has workstation necessities
This one is hard to say. I personally have never had any benefits from using a multi-gpu setup for non-game/benchmark software and had issues getting to them to work for video editing software (After Effects), or stuff like Photoshop. Then again my GPUs are not workstation cards but game oriented video cards. Since the new Mac Pro has two workstation GPU's it must be beneficial right?

Chromebook (C7) as a Media Server

XBMC Black Screen Bug caused by LucidLogix Virtu MVP

Taking Forever to Fix a Small Problem

Dual GPU Dilemma

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