iSCSI vs FC SAN

[SM_3]

How would you weigh up the pros and cons of iSCSI and Fibre Channel SAN?
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Thanks
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[Doug de Werd · Accepted solution]

Until full iSCSI support is incorprated into software and hardware, iSCSI is mainly used as a bridge technology. Currently the main benefit is that you can use standard ethernet cabling for iSCSI, where FC of course requires fibre cables. If you already have an installed base of FC products, then you would most likely stay with them, although you could use iSCSI as a bridge into your SAN. If you don't currently have FC, then it's more of a toss up. FC is probably going to be faster for now, but that will change as 10 GB ethernet and TCP offload engines become more prevalent.

There is some excellent info at this web link

http://searchstorage.techtarget.com/bestWebLinks/0,289521,sid5_tax401,00.html

Thanks,
Doug

[Mike Naime]

FC is what SAN was designed for. ISCSI is an add-on. As such, my personal opinion is that I only see iSCSI as a CON.

Why complicate matters by combining your storage network with your IP network? Especially in LARGE SAN fabric(s).

There are valid logical reasons why we have 4+ network backbones (Plus VLANS), and multiple SAN fabrics.

Too much in one basket is begging for unsolvable problems. What is your paranoia (Redundancy) level?

[Angus Crome]

I tend to take the wait and see approach with iSCSI. We have consolidated on FC (at least on the Unix side) and are very happy, however, we don't yet do remote mirroring. This is extremely expensive over Fibre-Channel, and I foresee iSCSI eventually replacing this, for both Native and bridging installations. I would agree with both replies above, TCP over 10Gb will probably blow-away 2Gb FC, however, I still expect that a good installation will still separate the general network from the (block or file)-system network.
That does not mean that both networks have to run at the same speed. I could see Gb Ethernet and 10Gb (Data) would probably handle darn near everyones needs for the foresee-able future. That said, smaller, faster and costlier does drive the technology jugernaut, so I'm sure faster protocols will come out before 2Gb is even mainstream. Sorry, went off on a tangent there.'

As for Pro's and Con's, right now, Block-IO is simply faster than file-io. If you need speed now, go with FC. If you want to look to the future, implement iSCSI on the front-end and have easier distribution. However, if you feel like taking a leap of faith, implement iSCSI now, it appears that the standards are in place, so it should be fully interoperable soon. I think it really depends on what your long term plans are. If you are going to have a small installation and not grow much in the next five years, then you can do anything and it will work great. If you plan on expanding, plan out which direction you want to go and design in some break-off points if one technology or the other goes the way of the dodo (not likely).