Daily Archives: November 28, 2011
I may be a bit “slow on the uptake”, but I’m struggling to understand industry claims that FCoE (Fibre Channel over Ethernet) is superior to having storage traffic sent over Fibre Channel. As a 34-year IT industry veteran and SAN storage specialist, it is my belief the only thing Ethernet data communications and SAN fabric transmissions may have in common is the label “network”. Therefore I’m puzzled why anyone feels “Unified Computing” is a more desirable solution for either Ethernet or SAN traffic. (Other than vendors who want you to buy their FCoE products.)
For the past couple of years we’ve been flooded with claims that “Unified Computing” (A.K.A. – Fibre Channel over Ethernet, or FCoE) is superior to separate Ethernet and SAN fabric networks. Webcasts and the trade press are awash with comments about the benefits and advantages of this new technology. If you believe everything you read, then FCoE should simply be sweeping the industry, making segregated Ethernet and SAN fabric channels a thing of the past. It’s not.
But will it? When I examined some of the claims in greater detail, they just don’t add up. The following is a matrix of popular “benefits” presented for FCoE, and my corresponding response as to why I question the validity of their claims.
|Reduces the number of adapters and cables that are deployed||On the surface this sounds logical, but it really doesn’t make much sense if you think about it. If a network (LAN or SAN) is designed for 30% average throughput with spikes of up to 70%, then it will still need (2) cables to support the configuration (70% + 70% = 140% of a single cable’s capacity). Unless your system is relatively small and/or the network is seriously underutilized, multiple cables will still be required. In addition FCoE will require some type of Quality-of-Service utility to ensure one service will not “starve” another, adding both additional complexity and greater expense.|
|Higher performance from 10Gbps network||This is also a compelling argument if performance is compared to 4Gbps Fibre Channel. But why, when 8Gbps FC is the current standard? Due to its more efficient protocol, 8Gbps performance is very similar to that of 10Gbps Ethernet. More significantly, now that 16Gbps Fibre Channel is shipping FCoE over 10Gbps Ethernet is the technology playing “catch up” now.|
|40Gbps and 100Gbps Ethernet interfaces are coming||This is a meaningless claim unless you’re doing extreme computing. 8Gbps Fibre Channel has been shipping for a couple of years, yet it is still being adopted at a leisurely pace. If there is no rush to upgrade from 4Gbps to 8Gbps FC (a 100% increase), why then will there be a rush to deploy 40Gbps Ethernet (a 400% increase) or 100Gbps (1000% increase) over 10Gbps Ethernet? Even 16Gbps Fibre Channel is a 160% over 10Gbps Ethernet.20Gbps and 40Gbps Infiniband have also been around for quite awhile. If raw channel speed is a major industry requirement, then why hasn’t Infiniband become a dominant network technology?|
|More efficient 64/66 encoding||If throughput is crucial, there is a logical argument for using 10Gbps FCoE (that uses 64/66 encoding) rather than 4Gbps or 8Gbps Fibre Channel (which has the less efficient 8/10 encoding). However, the latest 16Gbps Fibre Channel (and above) employs 64/66 encoding too, so this “benefit” is no longer relevant.|
|Greater flexibility||Hmmm… I’m not certain how merging two dissimilar technologies onto a single network medium will provide “greater flexibility”. In most cases just the opposite occurs.|
|Lower power and cooling||Since their component count, general circuit layout, and optical drivers are very similar, just what is it that makes FCoE have “lower power and cooling”? (Please don’t say that it’s because it needs fewer cables. Passive Fibre cabling really doesn’t consume much power!) 🙂|
|Simplified Infrastructure||This might be true, as long as you’re running low demand systems that only require a single cable. However, if traffic load needs two or more cables, then all bets are off.|
|Better compatibility with virtualized servers||Why? How is running multiple virtual servers over FCoE provide better compatibility than running multiple virtual servers over NPIV? What unique attribute is it that makes FCoE more compatible?|
|Availability of network security tools||This is an interesting argument. The reason we have more Ethernet security tools is that as an external facing technology, more people are trying to hack it. It is true that fibre channel has fewer security tools, but if they are sufficient to provide excellent storage security, why does having more of them matter?|
|Lower cost||Really? What numbers were they looking at? A quick search on Google Shopping shows both FCoE NICs and 8Gbps HBAs are in roughly priced the same.Several months ago we also estimated the total cost of an enterprise architecture using the both technologies, and found that the FCoE configuration ran about 50% higher than 8Gbps Fibre Channel! So much for being less inexpensive!|
|Familiarity within the enterprise||True, but what does familiarity have to do with it? There are lots of people familiar with copying data to DVDs, but that doesn’t make DVDs a better choice for data center backup and recovery. A specialized application like NetBackup or TSM will do a far better job of enterprise backup and recovery, even if only a few IT backup specialists are familiar with them. “Dumbing down” an IT operation to save money is a questionable tactic if user performance is sacrificed in the process.|
|Interface with the Cloud||In what way? The TCP/IP protocol is not native to WAN communications infrastructure, so 10Gbps Ethernet must be converted into something else on each end, just like Fibre Channel. For an internal Cloud connection, TPC/IP is not native to the SAN storage either, so 10Gbps Ethernet must be converted into a block storage format and back in the array, as well.|
|Simplified management and integration with tools||Whoever claimed this as a “benefit” apparently knew little about the breadth and depth of storage management tools available on the market today.|
|No proprietary tools needed to install||I have no idea what proprietary tools they’re referring to for installing Fibre Channel. Last time I did a Fibre Channel installation we used exactly the same tools that were used for high-speed Ethernet interconnections.|
|Lossless Ethernet||Hmmm… If I push the Ethernet standard far enough to compensate for its inherent “best effort” characteristics, doesn’t it just end up looking a lot like the Fibre Channel Protocol (Which is a well established, proven technology)?|
|Operational efficiencies and performance enhancements||If I run FCP (or any protocol) over any other protocol I incur two types of delays – conversion latency, and the consumption of extra CPU cycles. How does adding overhead improve either efficiency or performance?|
|People and skill consolidation||This is an argument typically presented by people with a limited understanding of the complexity of modern SAN storage. Ethernet LANs and SAN FC Fabric have very little in common, other than both support data traffic. Assigning Ethernet LAN specialists to manage enterprise SAN fabric makes no more sense than having SAN specialists manage corporate network communications.|
|Ubiquitous computing||This is a benefit? Stored data is the most valuable asset a corporation or Agency owns. While it may be important to offer ubiquitous computing to the user community, maintaining, protecting, and optimizing data assets should be carefully orchestrated activity provided by highly trained storage specialists!|
|Cost-effective network||Do your own comprehensive cost comparison and see if you agree. My estimate indicated identical functionality from 10Gbps FCoE would cost around 150% more than an equivalent 8Gbps Fibre Channel configuration.|
|Pervasive skill set||Like the “people and skill consolidation” myth above, this is based on a misguided assumption that operating a SAN fabric is somehow similar to operating an Ethernet data communications network. It is not.|
|Simplified interoperability||This may be true – if you can tolerate the latency and performance penalties associated with having one technology host another. As long as server farms are fairly small and storage requirements are modest, making performance compromises for the sake of convenience isn’t an issue. However, it rapidly grows in difficulty as stored data volume increases.|
|Reduces capital and operational costs||As above, do your own price estimates for identical functionality from 10Gbps Ethernet and 8Gbps FC. I think you may be surprised.|
What seems to be missing from these discussions is:
- Vulnerability created by having both data communications and storage traffic over the same medium. If there is an external attack on the Ethernet network, all computing activities will be brought to a halt. If there is a critical firmware bug, both data and SAN traffic is impacted. Troubleshooting becomes much more complex and time-consuming.
- The importance of keeping dissimilar technologies separate so they’re allowed to evolve at their own pace. If both storage traffic and data communications are dependent upon Ethernet, then each is constrained by the evolution of the other. If one requires more capacity and the other doesn’t, you’re forced to buy the consolidated infrastructure in its entirity.
- Dissimilar skill sets and areas of responsibility managed by different IT specialists. Ask most LAN specialists how to zone a fabric or allocate LUNs and you’ll get a blank stare. Ask most SAN specialists how the configure a router or use a packet sniffer, and you’ll probably get a similar response. SAN storage and SAN fabric management are activities that are inextricably linked. Splitting areas of responsibility between a LAN Group and SAN Group is a recipe for operational inefficiency, troubleshooting complexities, and reduced staff productivity.
- If industry adoption of FCoE has been widespread, then why do IT industry research Groups keep reporting sluggish sales? Also, why do Fibre Channel equipment sales remain robust?
I have no illusions there being lots of things I didn’t know, so I could be wrong about this too. If you feel there are other compelling reasons why FCoE will dominate the industry, I’d love to hear them.