iSCSI vs. FCoE

lamav · ‎06-06-2010

Hi:

Does anyone here have an informed opinion (probably through practical experience) regarding the iSCSI vs. FCoE speed debate going on? Which method of I/O consolidation and fabric unification is "better"? Of course each technology has its advantages and disadvantages...

I know that Cisco has invested a lot in FCoE and they have gotten large technology partners, like EMC, to join their caravan.

Please dont give me an explanation of each technology and a link to some resource. I know what each technology does and how it works. I am looking for informed opinion regarding performance.

Thanks

shamilton-wilkes · ‎06-07-2010

I think that in theory, provided there is no contention, there will be little if any real world performance difference between the two. - If in both cases the hosts have enough CPU/buffers/10 gig connectivity, there's no congestion in the network etc., the SAN has similarly no resource issues processing whichever protocol.

However, I think that in practice, FCoE is the better engineered protocol, just because the perfect world of the above is unlikely, and when congestion/contention occurs, FCoE will handle it gracefully.

I'm resisting linking you to lots of white papers on the relevant standards

Simon

bfeeny · ‎06-10-2010

FCoE is going to be fundamentally better as their is less overhead, and this is where the industry is going.

FCoE is not routable on its own however, so iSCSI is nice to connect initiators that don't have layer 2 adjacencies and environments where you don't have FCoE.

There are feature differences between the two as well. In raw performance I would say FCoE is going to be faster.

lamav · ‎06-26-2010

Thanks, folks.

I was sort of leaning in the direction of FCoE, too, until I did some more reading. With iSCSI, the packet size can be up to 9K Jumbo frames, whereas FCoE is only about 2.5K. Moreover, FCoE adds more header overhead with 3 layers of encapsulation. Lastly, with 3 of the 4 CEE standards ratified, it's iSCSI that will benfit the most from it, whereas FCoE cant live without it.

Just some thoughts.....

Victor