Question about bonding

[dweberwr]

I am hoping somebody can clear up my confusion. I am new to iscsi and understaning the whole deal about bonding nic's, so bear with me in my explanatio. I am looking at building a iscsi san box with 8 gbe ports on it. I will have at least 4 servers connecting to this san, maybe 2 more. My thoughts were to put a quad port card in all of the servers, connected to a dedicated gigabit switch for the san. What I was wanting to do was bond all 8 ports on the san and have each servers quad card bonded as well. At this time, I am not doing high availability or clustering. Eachserver will be connecting to its own target. Will this work to get the maximum performance out of the san and servers?

[enealDC]

You have some flexibility here.
A couple of things you should know. Bond's provide great fault tolerance but suck at providing additional performance. I would suggest you look into multipathing your targets across two or more interfaces.
IMO you need two switches and you don't really need more than two interfaces per initiator.

[webguyz]

The hardest thing to wrap your head around bonding is that is doesn't multiply your bandwidth. If you have 4 gigabit cards bonded together you will NOT get 4 gigabit of bandwidth. You will get load balancing across all 4 cards, but your performance will never be more then 1 gigabit, but you will have simultaneous traffic across all 4 channels.

Multipathing allows simultaneous access across 2 channels (or more) if you use Least Queue method of MPIO so it appears your getting more bandwidth but your really splitting the load

We have dual 10g cards in our 2 DSS's and just a single dual ethernet card dedicated for ISCSI in each server doing MPIO. We have 6 servers right now and never really strain anything and get good performance under Hyper-V

[cphastings]

Hey webguyz - are you running File or Block I/O under Hyper-V? I am running Block but I was curious what you were doing.

[dweberwr]

Ok, perhaps bonding wasn't the correct word. Seems like every manufacturer has a different definition bonding... So what I really am looking for is link aggregation. That would be 802.3ad?

[dweberwr]

Hey webguyz - are you running File or Block I/O under Hyper-V? I am running Block but I was curious what you were doing.

I am curious about this as well as I am running hyper-v.

[webguyz]

Doing File I/O but without write caching because of replication for autofailover. Took a perfomance hit when I had to turn it off. I tried it with Block I/O and couldn't see that much difference in performance.. Nothing scientific, just using HDtune Pro and the results were close in File I/O and Block I/O. I had write cache on the volumes at the time I was testing.