Hi,
On 16.03.21 03:40, Dave Hall wrote:
Andrew,
I agree that the choice of hash function is important for LACP. My
thinking has always been to stay down in layers 2 and 3. With enough
hosts it seems likely that traffic would be split close to evenly.
Heads or tails - 50% of the time you're right. TCP ports should also
be nearly equally split, but listening ports could introduce some
asymmetry.
Just a comment on the hashing methods. LACP specs does not include
layer3+4, so running it is somewhat outside of the spec.
The main reason for it being present it the fact that LACP load
balancing does not work well in case of routing. If all your clients are
in a different network reachable via a gateway, all your traffic will be
directed to the MAC address of the gateway. As a result all that traffic
will use a single link only.
Also keep in mind that these hashing methods only affect the traffic the
originate from the corresponding system. In case of a ceph host only the
traffic sent from the host is controlled by it; the traffic from the
switch to the host uses the switch's hashing setting.
We use layer 3+4 hashing on all baremetal hosts (including ceph hosts)
and all switches, and traffic is roughly evenly distributed between the
links.
Regards,
Burkhard
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