Thanks for the link , good price I have been watching these cards , but cables I found for them they're all expensive or I don't know how to find a matching cable for a direct link between the cards. I am sorry this is my first buying cards of this type. And since mu friend will bring them to Europe for me I must make sure I got all that I need. Prices here are much more then in US.
This is all very new to me, I have a Dell r710 and I probably would buy R520 unless I find r720 for good price but in Europe, so these cards will be used on them and mu win10 PCs. Servers are used for ESXI and will use them for data storage too.
Sorry for my low knowledge on this topic, but these cards would work without problems in the above specified computers?
Yeah, I don't see any reason why the NICs wouldn't work in your machines, they're standard PCIe. Just make sure you've got an 8x slot for them, I remember people mentioning that they get a little cranky at lower link speeds (they still work but speeds get weird.)
If you're just direct connecting two machines you can use a cheap NetApp DAC. These are intended for external NetApp SAS enclosures but they handle 40GbE perfectly:
netapp qsfp sas | eBay. They come in a variety of lengths so pick whatever length you think you need, they're dirt cheap too. I think all of mine were <$10/ea.
If you need or want to connect them to a 10Gb SFP+ switch you'll need an adapter for the port on the NIC but after that you can use standard 10Gb SFP+ optics or a DAC:
Mellanox 655902-001 655874-B21 HP QSFP/SFP ADAPTER 656541864054 | eBay. Look at different sellers for these, sometimes you'll find them for $7/ea shipped, other times you can Best Offer a better price than listed.
If you're linking Mellanox to Mellanox and both ends support FDR14 you can use an FDR cable and link at 56Gb, but they're expensive and for home lab level stuff there's rarely any benefit to the extra bandwidth:
Mellanox FDR 56Gb/s Passive Copper Cables - cable QSFP+ 1 m (MC220713-001 #88985 | eBay
I don't have anything other than Mellanox and Brocade 40Gb gear so I can't speak to issues with other brands, but I can tell you that both Mellanox and Brocade are extremely forgiving about optic and DAC brands so I haven't had any issues at all.