Fibre Channel or iSCSI

[ITaaP]

If I am building out a new infrastructure, why would I choose fibre channel over iSCSI? Obviously 16Gb/s FC has a higher possible throughput, but I have never seen a 10GbE or 20Gb LAG become fully saturated. Especially in a greenfield deployment when all the networking is being replaced too, it seems like 10Gb ethernet switches would be the most cost effective way to go. But yet I still see people deploying brand new fibre channel. Are there some benefits that I am not seeing?

Even SolidFire recently put out an article as to why they designed their storage using iSCSI.

[CalvinZito]

As long as you buy a network that is fast enough to meet your requirements, you can get what you need from iSCSI but it depends on a lot of different things. If you're comparing 16Gb FC to 10GbE, you'll have more headroom with a 16Gb FC SAN. 

Deciding whether iSCSI or FC SAN is right for you I think hinges on one big decision: do you have FC SAN expertise. Since an iSCSI SAN utilizes LAN technology, it tends to be better understood.  But even there, our FC SAN partner Brocade is doing a lot to make SANs easier to manage. 

I disagree with SolidFire that iSCSI is better. iSCSI SAN tends to be a bit simpler and maybe lower cost (when you compare similar speeds like 10GbE vs 8Gb FC) but the right choice for you depends on your unique requirements and what expertise you have in house. 

[Bart_Heungens]

Meanwhile 20GbE is available which makes the discussion about speeds versus 16GbFC useless... Will be almost the same...

However, iSCSI as protocol has more overhead sending a certain amount of data accross the cable which makes it less efficient. But I have a lot of customers running very happy on the iSCSI based StoreVirtual platform being performant and high available for their imoortant business applications...

The biggest challenge (don't want to call it a problem) I see today is the knowledge on networking... Ethernet seems simpler compared to FC networks but actually it isn't... I see too many configurations ending slow and unstable since the engineer is an expert in server and storage but not networking... And then you have to tell them about Flow Control, Jumbo Frames, Spanning Tree, trunks, switch stacking and so on...

Believe me sometimes I prefer to create a zone on a FC switch and move on with my real work... ;-)

Conclusion? Both are OK and mature, but it depends which one you know best...

[NirupakD]

Hi,

Leaving aside the techinical factors, speaking strictly from support perspective, a full FC SAN is a better option, if you can go for it. This ensures when you log a support ticket, it is easy to diagnose any issue with storage or fabric(SAN) since it is all FC. If however you have iSCSI topology, diagnosis involves multiple layers and switch technologies.

Also counting from experience, performance issues of badly designed iSCSI setups are not easy to overcome. This is not seen when the initial design is implemented, but over a period of time bottlenecks develop as the user implements different types of hosts and with them comes varied application. To mitigate these issues fine tuning of que depth and frame sizing is required. But that is easier said than done. For example if one host uses normal frames and other uses jumbo frames.