What is the difference between 10GB SFP+ and 8GB SFP?

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sthsep

Member
Mar 7, 2016
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Hello,

I snapped a bunch of cisco transceivers and in the package were also some 8GB SFP. I know that the SFP+ modules are used in ethernet and the 8G SFPs are used in FC/SAN-Networks. Since I just wanted the other transceivers I have left the 8GB ones for three days just in box.

Since they looked so similar I was thinking to test them in my Gnodal switch but I was pretty sure that they will not work (Because they are different and also they are using a different encoding). So I changed one finsar transceiver with on 8GB SFP and the link was going up?!?! Tested them with iperf and everything was nearly the same like the SFP+ transceiver before (I think they were a bit slower something like 9.6 vs 9.9 Gbit). Then I also changed the transceiver on the network adapter so it was then 8GB - 8GB and the switch turned the light to red so I think this way was not working.

Because I got the combination 8G SFP (Switch) --> 10G SFP+ (Network Adapter) working I was thinking what the real differences between this adapters are or also why I can use 8G SFPs in combination with 10G SFP+ without any problems? There are bunch of 8G SFP for arround 1 dollar per piece and they are really cheap compared to the 10G ones.
 
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i386

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Mar 18, 2016
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The sfp+ standard v4.1 (aka SFF-8431) supports up to 32 gbit/s for fibre channel and up to 10gbit for ethernet using the same connectors.
http://www.fluxlight.com/content/Tech-Docs/SFPPlus MSA.PDF , page 135

sthsep said:
Then I also changed the transceiver on the network adapter so it was then 8GB - 8GB and the switch turned the light to red so I think this way was not working.
Click to expand...
My guess is you didn't use a mellanox adapter which supports a lot more third party transceivers than intel or others.

sthsep said:
Because I got the combination 8G SFP (Switch) --> 10G SFP+ (Network Adapter) working I was thinking what the real differences between this adapters are or also why I can use 8G SFPs in combination with 10G SFP+ without any problems?
Click to expand...
There shouldn't be any difference as both use sfp+/sff 8431 at their physical layer. The problem is that some adapters check the rom on transceivers for certain strings. If the adapters don't find such a string in the rom, they will refuse to work with that transceiver and you will get no link.
 
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sthsep

Member
Mar 7, 2016
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So basically they are the same as long as the devices accept the transceiver right? Anyways I ordered already about 50 8G ones ;) And yes I wasn't using Mellanox adapters I was using some special card from Intel which should be like the Intel X-520
 
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Evan

Well-Known Member
Jan 6, 2016
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10G ethernet & 8G FC essentially the same thing from a technical point of view, all depends on compatibility. I have not tried any 10G ones but years ago 1G SFP I had used interchangeable ones.
Some adapter cards are actually dual configurable... FC, Ethernet, FCoE.

Let us know how you get on.
 
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Jerry Renwick

Jerry Renwick

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Aug 7, 2014
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Although there is little difference between 8G SFP anf 10G SFP+, it is still not recommended to use the adapters for this connection. Have tried the Mellanox QSFP top SFP+ adapter in my network, not happy with the high insertion loss.
 
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whitey

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Jun 30, 2014
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Jerry Renwick said:
Although there is little difference between 8G SFP anf 10G SFP+, it is still not recommended to use the adapters for this connection. Have tried the Mellanox QSFP top SFP+ adapter in my network, not happy with the high insertion loss.
Click to expand...
I dunno what this is abt but my MLX QSFP to SFP+ adapters push line rate 10G ethernet speeds and I do not see anything wonky on my physical 10G switch or errors/retransmits/packet loss, etc. Do tell?
 
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