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Hardware Thread, Fibre Channel interchagability, and iSCSI in Technical; Quick question 1): is 4Gb/s fibre channel interchangeable with 8Gb/s - IE will a 4Gb/s card (IBM) work on an ...
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    Fibre Channel interchagability, and iSCSI

    Quick question 1):

    is 4Gb/s fibre channel interchangeable with 8Gb/s - IE will a 4Gb/s card (IBM) work on an 8GB/s switch ?

    Quick Question 2):

    Which is faster 10Gb/s iscsi or 8GB/s FC ? The cost of a 10GB/s switch doesn't seem to be much more than 8GB/s FC.

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    Q2) Throughput or latency, FC is more efficient and quicker through the stack so for latency FC is faster, throughput will probably go to the 10GB but not by as much as the speed rating would lead you to beleive. It also depends heavily on the hardware at the other end as you need a SAN that can saturate the channels for any of this to be realavent.

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    CyberNerd (12th January 2012)

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    Quote Originally Posted by SYNACK View Post
    Q2) Throughput or latency, FC is more efficient and quicker through the stack so for latency FC is faster, throughput will probably go to the 10GB but not by as much as the speed rating would lead you to beleive. It also depends heavily on the hardware at the other end as you need a SAN that can saturate the channels for any of this to be realavent.
    VMWare is showing disk access as our current bottleneck. We're currently running 4GB/s FC onto 10k SAS drive SAN ( IBM DS3400 ). Looking at sensible upgrade paths, but keeping as much original equipment as I can.

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    10GB gear is much more reusable as you can push it into the network later on if it falls out of scope and the speeds are comparable.

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    Quote Originally Posted by CyberNerd View Post
    Quick question 1):

    is 4Gb/s fibre channel interchangeable with 8Gb/s - IE will a 4Gb/s card (IBM) work on an 8GB/s switch ?
    ^ Bump

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    My understanding is that a switch designed for 8gbps operation should be downward compatible with lower speed sfp's, my assumption is they just
    negotiate down to the lowest common speed in switch-to-host or switch-to-target connections. That was the case with 4/2/1 FC switches.

    although obviously best to consult the documentation for the fabric switch your looking at upgrading to.

    I'd be really surprised if the 4GB/s was the bottleneck, could be that you've got an entry level array and may need to think about upgrading to something
    a bit more midrange ? FC disks, more spindles etc.

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    thanks for that.

    VMware is certainly showing a bottleneck on disk I/O. it is an entry level DS3400, but im not in a position to upgrade that this year. I should be able to get the cash for server upgrades and was thinking about getting 8Gb FC in anticipation of upgrading the swich or SAN at a later date.

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    Speed wise 8gb fc and 10gb ethernet are pretty similar. If you don't currently have a fibre infrastructure (or your looking to upgrade to 8gb) I wouldn't bother. 16gb fc is now on the market, but 10gb ethernet is a much longer time investment. Tbh most large companies are looking at converged infrastructures and FCoE.

    Most of the new and innovative SAN products are now ethernet/iscsi/NFS based SANs. Products from NetApp, HP Lefthand, Dell Equalogic/Dell Compellent as well as the new smaller companies (Coraid, Kaminario, Tintri, Whiptail, Nimble etc) all fully support ethernet/iscsi. Personally I don't believe you need fibre channel any longer, and actually as Synack says 10gb ethernet gives you the ability to use it for other things should you need to.

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