04.08.2023 4:41, Alan Somers wrote: > On Thu, Aug 3, 2023 at 2:14 PM Eugene Grosbein <[email protected]> wrote: >> >> 04.08.2023 0:56, Alan Somers wrote: >> >>> I'm trying to build a high-speed iSCSI server. I have two Chelsio T6 >>> cards providing 4x 25GbE ports. I have a requirement for >>> high-availability networking, and I also need multiple ports' worth of >>> bandwidth. What's the best way to use them? >>> >>> First I tried LACP, of course. That works. But it doesn't work in >>> combination with cxgbei iSCSI offload. The clients can't connect. >>> This makes sense, because the offload engine probably requires all >>> packets from a single iSCSI session to enter and leave through the >>> same network port. With LACP, that won't be the case. >> >> This is a common misunderstanding. In fact, LACP has nothing to do with >> per-port >> traffic distribution. Used kind of hashing function is not a part of LACP. >> You just need to use link partners capable of good hashing. >> >> For example, FreeBSD lagg(4) hashing function is capable of using L2 (MAC), >> L3 (IP) and L4 (TCP/UDP ports) >> headers and any kind of combination of such headers to make sure that >> packets if single flow go out >> using same port. Take a look at ifconfig.8 manual page for "lagghash". > > For iSCSI, any combination of those hash settings should result in a > flow that is always tied to a single port. But for cxgbei to work, I > need to ensure that the switch also hashes flows in the same way, to > the _exact_same_port_. Even if I had access to the switch's LACP > configuration, which I do not (but perhaps could acquire), is there > any guarantee that it would hash things the same way as FreeBSD?
No. > Is the LACP hashing algorithm standardized? Hashing is not standardized. And hashing is not part of LACP, at all. LACP is not about hashing.
