Questions regarding 2nd gen CNA adapters in Linux servers
 

I am curious is anyone is currently running an FCoE environment in their data center. We are in the processes of setting up a new computing on demand (CoD) environment at my work and are utilizing the brand new 2nd gen CNA modules for the Dell Bladecenter from Emulex. (OneConnect is what they're calling the new stuff.) We've had a lot of issues from day one, but now that we've mostly got the CNA functional on a physical Linux blade (RHEL5.5) I am very curious about the slow (to me, at least) transfer speeds we are seeing to the SAN. I am not a network or SAN expert, I stick with the Linux OS side of things, hence my coming here. We are seeing maybe 20mb/sec when writing to the SAN. At the same time I'm getting MASSIVE amounts of RX overruns. (After copying around 40gigs of data I had over 2 million RX overruns.)

We are working directly with Emulex on this, as this hardware is still so new. What I'm getting back from them though, is that 20-30mb/sec write to the SAN (single LUN) is normal, and that the overruns may be a 'reporting error.' I haven't had a chance to go back to an older system with an older Q-Logic HBA in it to do any speed tests, but this just doesn't seem quite right to me. (My cheap-o internal SATA drives in my home pc can do 30-50meg/sec of write.)

My real question, I guess, is for anyone running an FCoE environment, what are typical write speeds to the SAN from a Linux box? The Emulex guy seemed to make a big deal that the linux box would be _slower_ than the Wintel box in this regards, which I also didn't quite understand.

Wow.. we really are the only people using these 2nd gen cards, eh?

Sounds to me like you might need to adjust some settings with regards to the tcp stack. Also look into the queue depth allowed by the card and the SAN. I know in our environment we adjust the queue depth to maximize our performance to the SAN.

The documentation on your card, and some digging would probably lead you to some better performance.