so there is FDR14 (for 56G) and FDR10 for 40G with less overhead? But FDR10 has higher cable requirements?
Kind of.
FDR uses a 64b/66b encoding in opposite to QDR which uses a 8b/10b encoding, so FDR is naturally more efficient.
However, 40G QSFP+ is generally QDR, so the electronics inside standard 40G QSFP+ cables only reports QDR in its capability list, so the card decides to use QDR.
100G, in opposite, is FDR, so the card decides to use FDR, but with a reduced data rate of 10G per lane (even though the cable technically supports more), because the cable needs to have a special coding (basically a license) that unlocks 14G FDR.
I haven't tested Mellanox 100G Infiniband cables yet (Mellanox has 100G Ethernet and 100G Infiniband cables), but at least for Mellanox 100G Ethernet cables, you only get FDR10.
(at least that's my theory and experience. I'm very interested in testing and verifying this further)
ok, I think you talked me into it. However, as I'm in Israel, going to have to see if my father is up for a project to test things out in the US before this is put on a container for me to Israel (have 2 DL380p g8's heading his way, so should have a testbed for testing.
As far as I remember, there were also pretty cheap offers from Israel! Just keep your eyes open.
Also there's a good stock of other Mellanox hardware in Israel sometimes.
