Date: Fri, 4 Aug 2023 06:27:37 +0700 From: Eugene Grosbein <eugen@grosbein.net> To: Alan Somers <asomers@freebsd.org> Cc: FreeBSD <freebsd-stable@freebsd.org> Subject: Re: Best practices for cxgbei and link aggregation? Message-ID: <4b9141b2-3d0d-955f-e11c-ff5291543cdd@grosbein.net> In-Reply-To: <CAOtMX2h41y84L_T-T1WhiA9DC93y3dQEZW=M3kj4JrAQGZTUpA@mail.gmail.com> References: <CAOtMX2jkwFXrjby7W-xyLSDUXhAwRKyrpBFTBMbD1pqQz9Z76g@mail.gmail.com> <708494cd-9c88-974e-da5f-1e8c1f270950@grosbein.net> <CAOtMX2h41y84L_T-T1WhiA9DC93y3dQEZW=M3kj4JrAQGZTUpA@mail.gmail.com>
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04.08.2023 4:41, Alan Somers wrote: > On Thu, Aug 3, 2023 at 2:14 PM Eugene Grosbein <eugen@grosbein.net> 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.home | help
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