Plummeting performance

[amandyke]

Looks like the other thread got locked before I could post with some screen shots of those sysctls in action.

Here are a few screen shots from my freenas box showing throughput using the sysctls Epac listed in the recently closed thread.

BuildFreeNAS-9.2.1.7-RELEASE-x64 (fdbe9a0)
PlatformIntel(R) Pentium(R) CPU G3420 @ 3.20GHz
Memory16040MB
System TimeSat Sep 13 15:13:20 PDT 2014
Uptime3:13PM up 32 days, 20:27, 0 users

16GB non-ecc ram running on an Asrock H97M Pro4 motherboard. It actually has an onboard Intel Nic, but the chipset is not supported in FreeBSD 9.x.

Certainly seems to be going fast enough for me. That's about as close to gigabit as is really necessary.

 

[jgreco]

The Realtek thing is basically a function of multiple issues. Some of the Realtek chips are really bad. Some will work "okay" as long as you can throw some significant amount of CPU grunt at them (like a 3.2GHz Haswell dual core).

I would like to inform everybody that you DO NOT need an Intel NIC in order to take advantage of your Gbps connection, even though other moderators/admins on this forum would like you to believe that Intel NICs are the only way to go. I have applied two sysctls on multiple FreeNAS boxes, in addition to sharing this information with colleagues, so I do know that these settings are effective.

This is simply a highly slanted version of what I summarized above. The part that's left out: Given a mainboard/CPU combo that can just barely achieve gigabit with an Intel card, there is NO WAY IN HELL the Realtek will come close to gigabit. Period. The Intel cards have a lot of chipset offload and highly tuned driver advantages.

It's also unfair to paint us "moderators/admins" in this light. From our point of view, we understand that the Realteks are inferior and we've seen so many cases where simply replacing the deficient part fixes the problem. Could we spend hours trying to help each poster individually to find more optimized settings for their use case? Possibly. But we're volunteers. A $30 quick fix is a $30 quick fix.

The suggested sysctl settings could be helpful for some subset of FreeNAS installs, but it is merely changing the TCP send and receive window sizes, so it is among the most naive of tuning strategies. What you really need to do is to walk through the various layers and spend some time analyzing what is contributing to the slowdown, including other changes to the network stack (many of which are already tweaked by autotune), then changes that are specific to each protocol and client combination. You CAN probably make many Realtek systems work much better, but it is going to be specific to each system and the details. For me, I can't justify spending lots of time to do that, when a $30 fix is available. And leaving snippy responses about how the moderators encourage people to buy the stuff we know is going to work well, that's not helping either.

Leaving the thread locked because, as cyberjock noted, this basically isn't likely to become productive. That being said, anyone who wishes to become the resident Realtek expert is ABSOLUTELY WELCOME TO. I will even buy you a helmet so that when you're beating your head against the wall, you survive a bit longer...