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BenHacker

iSCSI or FCoE?  That is the Question...

Posted by BenHacker in The Data Stack on Mar 16, 2009 5:07:51 PM

The storage world is getting quite a bit of press lately. As IT organizations seek to reduce costs, streamline their management tasks, save power, increase capacity and access to their data and improve security, new types of storage solutions are being introduced continuously The growth rate of storage revenue is blistering, and the number of companies scrambling for the piece of the pie is impressive.

 

As with any hot area of technology, there are a lot of technological developments to keep track of, and of course there are disputes about which new trends will maintain dominance, and which technologies will end up carrying the day. I’ve writtenin the past about some of the potential improvements coming along with the introduction new Data Center Ethernet (DCE) [aka, Data Center Bridging (DCB)] IEEE standard improvements. These layer 2 improvements coupled with Fiber Channel over Ethernet (FCoE) can bring to the storage world a converged story for networking. However, noticeably missing from my previous post was a discussion of iSCSI. The iSCSI standard has been around since 2003, and many vendors including Intel have been selling adapters with various levels of support for iSCSI for quite some time. Microsoft has an iSCSI initiator built into their server OS stack, and VMWare also supports iSCSI in their virtualized system environments. This isn’t a comprehensive list, but just a summary to show that iSCSI is ‘real’.

 

So the question is how does FCoE fit in with iSCSI? Are they competing technologies, or complimentary, or neither? Did I leave iSCSI out of my earlier discussion because I believe the technology is doomed? Hardly…

 

The basic case for FCoE is pretty straight forward. If you have an FC SAN in your datacenter, as you roll out a new rack (for instance) you can eliminate the top-of-rack FC switch and also the need for two adapters in each of servers (one for Ethernet, and one for FC). There are additional potential savings as you move FCoE further and further into the network, but I think to keep the discussion simple, the key thing to note is “if you have an FC SAN…”; then you care about FCoE and can potentially gain from it. If you don’t, well then FCoE will not necessarily be your technology of choice. FCoE is not an Ethernet capability that will drive you to use Fiber Channel, but it may make expanding and growing your FC network cheaper, lower power, and more convenient, especially with virtualized blade servers.

 

To elaborate, today the iSCSI SAN market is growing quickly, but it is growing in areas where FC is not generally a popular solution. It is usually chosen where storage over IP on existing Ethernet was viewed as acceptable given the cost tradeoffs. In contrast, FC is deployed where key IT knowledge, and its higher cost hurdles are still overcome by its performance and high reliability; this is generally only the case in fairly large datacenters. iSCSI on the other hand tends to be used in smaller enterprises and potentially in Tier 2/3 datacenters. The question of iSCSI or FC/FCoE is likely not getting decided by the network card in the host initiator. It is decided by organizational needs, and the cost structure / ROI of the storage target deployment including IT personal / expertise. If an organization has FC deployed, FCoE makes sense. If you are designing a new datacenter, FCoE isn’t exactly going to drive your decision (although you may still want to use it). The better way to consider FCoE is that it is another storage over Ethernet option, specifically for FC (to add to iSCSI and NAS). So decide which is the best storage system solution for your Data Center and know that you can connect any of these solutions over Ethernet to your servers.

 

Finally, as the improvements in Ethernet proliferate and these DCE capabilities become mainstream the landscape may change for iSCSI and FC deployments, but the simple fact is that in most cases, the main commonality is that Ethernet is chosen fabric to deliver storage over the network. Whether the storage protocol that is used is iSCSI, or FCoE will be determined by a lot of things within an individual companies’ IT shop. The idea that iSCSI and FCoE are a pair of competitive technologies has been raised in various places around the tech industry, but in reality, these arguments are driven more by people who have some bias toward one solution or the other, it is not fundamentally driven by the end user demands for storage. Both technologies have their place, and both will be supported in varying ways by Intel as well as other ecosystem vendors in the future.

 

So iSCSI or FCoE? I think the answer is: Both.

 

As we move to 10 Gigabit networking, IT decision makers will have something great with both of these capabilities; convergence, and choice. Only Ethernet can deliver this.

 

 

Ben Hacker

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