The SNIA Solid State Storage Initiative (SNIA SSSI) is working to better understand disk drive use in everyday computer actions. You can help by participating in our Workload I/O Capture Project - WIOCP - and get rewarded!   The WIOCP captures I/O statistics unobtrusively and without compromising your PC’s performance. No personal data or content is captured - only statistics on the types of data transfers that occur.  This helps the SNIA SSSI and the industry understand what actually takes place with your drive when you use your PC.   Collecting I/O statistics helps computer scientists determine the type of workloads your drive is experiencing.  By capturing statistics from a large number of computer users, designers can optimize both the drive and the host computer system to improve your overall computing experience.  You can be a part of history!   Participate NOW and return one set of statistics to qualify to win a $10 Amazon gift card and to be  entered in a drawing for a free Intel 120GB SSD.  Submit more sets and increase your chance of winning a SSD!   Go to http://www.snia.org/forums/sssi/wiocp for a FAQ and details on participating.  And see results at http://iotta.snia.org/

The SNIA Solid State Storage Initiative (SNIA SSSI) is working to better understand disk drive use in everyday computer actions. You can help by participating in our Workload I/O Capture Project – WIOCP – and get rewarded!

 

The WIOCP captures I/O statistics unobtrusively and without compromising your PC’s performance. No personal data or content is captured – only statistics on the types of data transfers that occur.  This helps the SNIA SSSI and the industry understand what actually takes place with your drive when you use your PC.

 

Collecting I/O statistics helps computer scientists determine the type of workloads your drive is experiencing.  By capturing statistics from a large number of computer users, designers can optimize both the drive and the host computer system to improve your overall computing experience.  You can be a part of history!

 

Participate NOW and return one set of statistics to qualify to win a $10 Amazon gift card and to be  entered in a drawing for a free Intel 120GB SSD.  Submit more sets and increase your chance of winning a SSD!

 

Go to http://www.snia.org/forums/sssi/wiocp for a FAQ and details on participating.  And see results at http://iotta.snia.org/

The Internet Engineering Task Force is one of the older – and more unusual – internet organizations. It first met in 1986, and has regularly met since then several times a year. The last meeting was the March 2-7, 2014 IETF89 in London,  and I was fortunate to be in attendance.

What Makes the IETF Unique

What’s unusual about the IETF? From my perspective as someone who spends most of his working day dealing with more traditional standards bodies, two things stand out.

One, (in its own words) “it exists as a collection of happenings, but is not a corporation and has no board of directors, no members, and no dues.” The non-members divide themselves into loosely organized groups that agree on an agenda, discuss the stuff of the internet on mailing lists, generate documents that reflect consensus, and then agree to them as standards.

Two, the London IETF89 meeting was not a conference. The IETF doesn’t do conferences; there are no formal papers given by luminaries or industry experts. There is an agenda, agreed beforehand by consensus (there’s that word again) and then a few short and brief presentations on topics of interest. There are questions from the floor, discussions, and agreement of one form or another. I didn’t see a single formal vote; just that ill-defined and unquantifiable consensus where the outcome is just, well, agreed on.

Why the IETF Works

Revolution! Anarchy! This is unusual for a standards body, and it sounds like a recipe for disaster. But strangely, it isn’t, and from what I saw of the process, I think I see why.

It’s because it’s attended by software and network engineers who see code as the concrete representation of a good idea. They value running code, or stuff that works. That’s a powerful advantage over academic discussions, or codifying and formalizing a good (sometimes not-so-good) idea that no-one has yet implemented or is ever likely to.

Why face to face though? I reckon that even revolutionaries and anarchists need validation and a sense of community, and there was much of that in evidence in the corridors and public spaces outside of the formal meeting. Everyone talks like there’s no tomorrow. Ideas everywhere, grounded in what can be shown to actually work.

I attended, amongst others, the NFSv4 workgroup meetings. The agenda and notes from the meeting give some flavor of this consensus, and I am truly impressed by the process. I’m also thankful that there is some organization; Sorin Faibish (EMC) took notes, Tome Haynes (NetApp) chaired the meeting and kept it moving along, and all in all it was a great illustration of the best the industry can do.

As to the technical content… well, you can read the minutes. There are notes on security discussions led by Andy Adamson, on features proposed for NFSv4.2, and getting an RFC in place that accurately reflects implementations of earlier versions of NFSv4 and more. I’ll be blogging about this and more over the next few months. In the meanwhile, in the spirit of the IETF that favors working code over ideas and the concrete over the abstract, I’ll be presenting “Practical Steps to Implementing pNFS and NFSv4.1” at DSIcon on April 22-24 in Santa Clara, CA. OK, this one’s a conference, and anarchy will be in short supply, but we can still have great discussions and arguments in the corridors and public spaces outside of the formal meetings. I look forward to seeing you there!

The Internet Engineering Task Force is one of the older – and more unusual – internet organizations. It first met in 1986, and has regularly met since then several times a year. The last meeting was the March 2-7, 2014 IETF89 in London,  and I was fortunate to be in attendance. What Makes the IETF Unique What's unusual about the IETF? From my perspective as someone who spends most of his working day dealing with more traditional standards bodies, two things stand out. One, (in its own words) "it exists as a collection of happenings, but is not a corporation and has no board of directors, no members, and no dues." The non-members divide themselves into loosely organized groups that agree on an agenda, discuss the stuff of the internet on mailing lists, generate documents that reflect consensus, and then agree to them as standards. Two, the London IETF89 meeting was not a conference. The IETF doesn't do conferences; there are no formal papers given by luminaries or industry experts. There is an agenda, agreed beforehand by consensus (there's that word again) and then a few short and brief presentations on topics of interest. There are questions from the floor, discussions, and agreement of one form or another. I didn't see a single formal vote; just that ill-defined and unquantifiable consensus where the outcome is just, well, agreed on. Why the IETF Works Revolution! Anarchy! This is unusual for a standards body, and it sounds like a recipe for disaster. But strangely, it isn't, and from what I saw of the process, I think I see why. It's because it's attended by software and network engineers who see code as the concrete representation of a good idea. They value running code, or stuff that works. That's a powerful advantage over academic discussions, or codifying and formalizing a good (sometimes not-so-good) idea that no-one has yet implemented or is ever likely to. Why face to face though? I reckon that even revolutionaries and anarchists need validation and a sense of community, and there was much of that in evidence in the corridors and public spaces outside of the formal meeting. Everyone talks like there's no tomorrow. Ideas everywhere, grounded in what can be shown to actually work. I attended, amongst others, the NFSv4 workgroup meetings. The agenda and notes from the meeting give some flavor of this consensus, and I am truly impressed by the process. I'm also thankful that there is some organization; Sorin Faibish (EMC) took notes, Tome Haynes (NetApp) chaired the meeting and kept it moving along, and all in all it was a great illustration of the best the industry can do. As to the technical content... well, you can read the minutes. There are notes on security discussions led by Andy Adamson, on features proposed for NFSv4.2, and getting an RFC in place that accurately reflects implementations of earlier versions of NFSv4 and more. I'll be blogging about this and more over the next few months. In the meanwhile, in the spirit of the IETF that favors working code over ideas and the concrete over the abstract, I'll be presenting "Practical Steps to Implementing pNFS and NFSv4.1" at DSIcon on April 22-24 in Santa Clara, CA. OK, this one's a conference, and anarchy will be in short supply, but we can still have great discussions and arguments in the corridors and public spaces outside of the formal meetings. I look forward to seeing you there!

As one Cisco colleague once said to me, “After the nuclear holocaust, there will be two things left: cockroaches and Ethernet.”  Not sure I like Ethernet’s unappealing company in that statement, but the truth it captures is that Ethernet, now entering its fifth decade (wow!), is ubiquitous and still continuing to advance at a breathtaking pace.  And as it advances, it advances the capabilities of storage networking based on the Ethernet backbone, be it file storage like NFS or SMB or block storage like iSCSI or FCoE.

Most recent evidence of Ethernet’s continuing and relentless evolution is illustrated in the 28 March 2014 announcement from the Ethernet Alliance congratulating the IEEE on formation of their IEEE P802.3bs™ Task Force:

The new group is chartered with the development of the IEEE P802.3bs 400 Gigabit Ethernet (GbE) project, which will define Ethernet Media Access Control (MAC) parameters, physical layer specifications, and management parameters for the transfer of Ethernet format frames at 400 Gb/s. As the leading voice of the Ethernet ecosystem, the Ethernet Alliance is ideally positioned to support this latest move towards standardizing and advancing 400Gb/s technologies through efforts such as the launch of the Ethernet Alliance’s own 400 GbE Subcommittee.

Ethernet is in production today from multiple vendors at 40GbE and supports all storage protocols, including FCoE, at those speeds.  Market forecasters expect the first 100GbE adapters to appear in 2015.  Obviously, it is too early to forecast when 400GbE will arrive, but the train is assuredly in motion.  And support for all the key storage protocols we see today on 10GbE and 40GbE will naturally extend to 100GbE and 400GbE.  Jim O’Reilly makes similar points in his recent Information Week article, “Ethernet: The New Storage Area Network” where he argues, “Ethernet wins on schedule, cost, and performance.”

Beyond raw transport speed, the rich Ethernet infrastructure offers techniques to catapult your performance even beyond the fastest single-pipe speed.  The Ethernet world has established techniques for what is alternately referred to as link aggregation, channel bonding, or teaming.  The levels available are determined by the capabilities provided in system software and what switch vendors will support.  And those capabilities, in turn, are determined by what they respectively see as market demand.  VMware, for example, today will let you bond eight 10GbE channels into a single 80GbE pipe.  And that’s today with mainstream 10GbE technology.

Ethernet will continue to evolve in many different ways to support the needs of the industry.  Serving as a backbone for all storage networking traffic is just one of many such roles for Ethernet.  In fact, precisely because of the increasing breadth of usage models Ethernet supports, it will also continue to offer cost advantages.  The argument here is a very simple volume argument:

Total Server-class Adapter and LOM Market Ports

Enough said, except to also note that volume is what funds speed roadmaps.

 

 

As one Cisco colleague once said to me, "After the nuclear holocaust, there will be two things left: cockroaches and Ethernet."   Not sure I like Ethernet's unappealing company in that statement, but the truth it captures is that Ethernet, now entering its fifth decade (wow!), is ubiquitous and still continuing to advance at a breathtaking pace.   And as it advances, it advances the capabilities of storage networking based on the Ethernet backbone, be it file storage like NFS or SMB or block storage like iSCSI or FCoE. Most recent evidence of Ethernet's continuing and relentless evolution is illustrated in the 28 March 2014 announcement from the Ethernet Alliance congratulating the IEEE on formation of their IEEE P802.3bsâ„¢ Task Force: The new group is chartered with the development of the IEEE P802.3bs 400 Gigabit Ethernet (GbE) project, which will define Ethernet Media Access Control (MAC) parameters, physical layer specifications, and management parameters for the transfer of Ethernet format frames at 400 Gb/s. As the leading voice of the Ethernet ecosystem, the Ethernet Alliance is ideally positioned to support this latest move towards standardizing and advancing 400Gb/s technologies through efforts such as the launch of the Ethernet Alliance's own 400 GbE Subcommittee. Ethernet is in production today from multiple vendors at 40GbE and supports all storage protocols, including FCoE, at those speeds.   Market forecasters expect the first 100GbE adapters to appear in 2015.   Obviously, it is too early to forecast when 400GbE will arrive, but the train is assuredly in motion.  And support for all the key storage protocols we see today on 10GbE and 40GbE will naturally extend to 100GbE and 400GbE.   Jim O'Reilly makes similar points in his recent Information Week article, "Ethernet: The New Storage Area Network" where he argues, "Ethernet wins on schedule, cost, and performance." Beyond raw transport speed, the rich Ethernet infrastructure offers techniques to catapult your performance even beyond the fastest single-pipe speed.   The Ethernet world has established techniques for what is alternately referred to as link aggregation, channel bonding, or teaming.   The levels available are determined by the capabilities provided in system software and what switch vendors will support.   And those capabilities, in turn, are determined by what they respectively see as market demand.   VMware, for example, today will let you bond eight 10GbE channels into a single 80GbE pipe.   And that's today with mainstream 10GbE technology. Ethernet will continue to evolve in many different ways to support the needs of the industry.   Serving as a backbone for all storage networking traffic is just one of many such roles for Ethernet.   In fact, precisely because of the increasing breadth of usage models Ethernet supports, it will also continue to offer cost advantages.   The argument here is a very simple volume argument: Total Server-class Adapter and LOM Market Ports Enough said, except to also note that volume is what funds speed roadmaps.    

We had a tremendous response to our recent Webcast “Use Cases for iSCSI and FCoE – Where Each Makes Sense.” We had a lot of questions that we didn’t have time to address, so here are answers to them all. If you think of additional questions, please feel free to comment on this blog.

Q. You stated that FCoE requires End to End DCB connectivity.  That is not entirely true if you have native Fibre Channel storage. 

Once native FC is added, it is a hybrid FCoE/native FC network, not a simple FCoE network.  To be clearer I could’ve stated that for FCoE all Ethernet links traversed must be DCB enabled.

Q. Any impact on the protocol choice if you bring SDN solutions with overlay networks using VXLAN or NVGRE within virtual switching in hypervisors into the picture?

An excellent question, but complicated enough that it probably deserves a discussion on its own.  Overlay networks encapsulate Ethernet frames into routable packets.  On a view of strict adherence to ISO ordering, that means L2 constructs like Data Center Bridging become “invisible” until decap.  You lose the “lossless,” low-latency that FCoE expects and iSCSI may be taking advantage of, depending on your implementation.  That doesn’t really favor one protocol over the other, but FCoE may lose advantages it has over iSCSI when confined to a single L2 subnet.  But, unfortunately, the real answer to your question requires that you investigate in detail how the system software you are using handles encapsulated storage packets for both block storage protocols.  Microsoft’s Hyper-V is different from VMware’s vSphere, and each flavor of SDN could be different as well.  Proceed with caution.

Q. Have you heard of any enterprise customers who are interested in NIC Partitioning to separate iSCSI, FCoE, and typical network traffic?  If so, can you provide information about those customers’ use cases?

We have not come across many customers that are interested in large-scale deployments yet.

Q. What are the use cases for using standalone FCoE switches in SAN keeping aside Cisco UCS and Blade Servers?

There are two ways to look at this:

1) To use FCoE as an end-to-end (Initiating server to target storage array) solution instead of, or to replace, Fibre Channel. Although, not very prevalent to date, the reason this option is chosen is to create a single converged LAN/SAN network that essentially retains the native FC constructs. The potential benefit would be in reduction in the amount of equipment required and the resources needed to deploy and administer two separate networks. This can be done in a phased approach, that uses multiprotocol switches, able to be used as Ethernet, FC or both on every port.  This will provide future proofing, reduced qualification costs, and lower OPEX by no longer requiring the purchase of multiple switches of different protocols.

2) To continue the use of FC for connectivity from the Top of Rack switch to the storage arrays, but use FCoE connectivity for server access. This is much more prevalent, and even when deployed outside of the Cisco UCS blade servers, is used to increase flexibility in highly virtualized server environments or multi-tenancy, where workloads/VMs from the same physical servers need to connect to different storage types.

Q. How do iSCSI and FCoE switches handle redundancy?  With FC, it is a best practice to implement dual fabrics with each storage system and server with paths down each.

Physical topology can be identical.  A storage system has one set of targets (either IP addresses or FCoE targets) on one switch and other targets on the other switch.  The initiators are configured to see any targets available on that leg.

To prevent Ethernet broadcast storms, technologies like per VLAN Spanning Tree and link aggregation are used.  TRILL can also be used.  For more details, I recommend reading this blog post by J Metz of Cisco.  http://blogs.cisco.com/datacenter/understanding-fcoe-and-trill-the-easy-way/

Q. Doesn’t increasing CPU mean software processing for FCoE and iSCSI at both endpoints can reduce costs considerably (i.e. no full HBA functionality needed at the endpoints)?

Absolutely.  If you have CPU cycles to spare at both endpoints, there is no reason to take on the extra cost of offload.  However, remember the principle behind Moore’s law also works on things like network adapters and HBAs.  It isn’t unreasonable to think that full offload capabilities will be included by default in a few years as technology progresses.  And even if they aren’t, the actual application of Moore’s law will push the difference in CPU utilization to be trivial.

Q. How do large data centers configure and manage iSCSI?  Is it by configuring the initiators and targets? My understanding is that most installations don’t use iSNS.  Is this true?

It is true that most implementations of iSCSI don’t use iSNS.  iSCSI initiators are simply configured with the target address by the administrator.  In the FC world, SNS is simply there, but the iSCSI equivalent, iSNS, has always been optional.  (SNS stands for Simple Name Service.  It is a service that helps initiators find targets.)

Q. I have been doing a lot of testing to compare iSCSI to FC and noticed that as we move from traditional storage to SSD-based storage the IOPS increase faster for FCoE. For example, 18K+ for FCoE vs. 12K for iSCSI. Have you seen similar results?

I have seen some similar results. However, I’ve also seen some that don’t necessarily line up with that.  I haven’t had the time to research this topic.  Sounds like a good topic for a future post.

Q. Do you have any information about the number of customers who use FCoE Boot and iSCSI Boot?

Unfortunately I don’t.  I do have anecdotal evidence to support customers using full-offload are more likely to boot from SAN.  Since more full-offload FCoE adapters are in use that full-offload iSCSI adapters today, it makes sense that more are booting over FCoE than iSCSI, but again, I don’t have any evidence to support that.

Q. What about iSCSI over RoCE?

There are three network/fabric technologies that use RDMA: InfiniBand, iWARP, and RoCE.  You can run iSCSI over any of these using the open-source iSER code supported by the Open Fabrics Alliance (https://www.openfabrics.org ).  iSER has been written to OFA’s “verbs” for RDMA (rather than to the more familiar “sockets).  However, note that of these three underlying transports, only iWARP is truly routable in general.  So technically you could implement iSER on InfiniBand or RoCE but it may not do for you what you expect iSCSI to do for you, i.e., go anywhere the internet goes.

Q. How does FCIP compare with iSCSI for long distance requirements?

FC networks rely on guaranteed packet delivery to deliver low latency, predictable performance. IP networks are a best effort network allowing for dropped packets with transmission retries. Given the possibility of latency loss, FCIP has experienced limited adoption. Useful where required. But, typically not a core part of infrastructure. If cost is a concern and long distance is required as part of the solution, then iSCSI is the better choice as it designed to allow for lossy networks. 

Q. Slide 22 – Was that hardware based iSCSI or software based iSCSI?

What was shown in the chart was software-based iSCSI, however you would see similar results with hardware-based iSCSI.

Q. What about FC vs FCoE performance? Any numbers?

Both Fibre Channel and FCoE can achieve line rate.  Here’s an example of testing Yahoo! did on an 8Gb FC HBA and a 10 GbE CNA that showed exactly that result: http://www.intel.com/content/www/us/en/network-adapters/10-gigabit-network-adapters/10-gbe-ethernet-yahoo-case-study.html .  So as Fibre Channel moves to 16 Gbps, it will outperform a 10GbE CNA, at least for peak performance.  However, the tables turn with a 40 GbE CNA, several of which are in production now.

Q. Do you see SR-IOV used currently or in the future to separate FCoE or iSCSI from standard LAN traffic?

So far we have seen that with the exception of a few operating systems (e.g., AIX), SR-IOV support today is network only.  Additionally, most customers want guaranteed bandwidth for storage and they wouldn’t be willing to run it on the same port as heavy NIC traffic.

Q. Are you aware of any FCoE targets for Windows?

I’m not aware of any right now.

Q. What is the max IOPS (at 4K) you can push thru 10G FCoE and iSCSI? Max latency (at 512 bytes)?

Latency is not determined by the pipe.

Q. Does FCoE really require a CNA? What about software only FCoE drivers?

Open FCoE does exist, but most FCoE implementations today use CNAs.  I do expect the adoption of FCoE software solutions to increase fairly substantially.  A lot of it comes down to the choice of booting via FCoE or another method.

Q. Do you think that the difference in FCoE/iSCSI usage for different App tiers can be related to the performance of the protocols?

Objectively, no.  Either protocol implemented can be configured to hit or exceed a performance number.  In my opinion, market perception of the protocols has more to do with the tier assignment than anything technical.

Q. Doesn’t 32 GbFC make it competitive with 40GbE FCoE?

From a purely technical perspective it helps, but FCoE is often deployed to reduce costs by simplifying cabling and switching by converging IP and storage onto the same fabric.  32Gb FC is slower than 40Gb and does nothing to reduce costs.  Unless 32Gb FC is significantly less expensive than 40 Gb Ethernet on a per port basis, market forces are going to push towards Ethernet.  There are still plenty of cases where organizations may deploy 32Gb FC instead of FCoE, but again, those criteria will mostly be non-technical.

Thanks to all my SNIA-ESF colleagues and Dell’Oro Group for helping me with these answers. If you missed the original Webcast, you can watch it on-demand here. You can also download a copy of the slides.

Join SSSI members for an "open" call on March 10, 2014 at 7:00 pm ET/4:00 pm PT.  SSSI member Jerome McFarland, Principal Product Marketer at Diablo Technologies, will talk about how memory channel storage technology works, how it's deployed, and its advantages for applications. Dial in at 1-866-439-4480 passcode 57236696.  A WebEx will be available at http://snia.webex.com, meeting number 792 152 928, password sssipcie. The SSSI PCIe SSD Committee is a SSSI member committee that provides guidance to the marketplace on SSDs.  This can take the form of educational materials, best practices documents, and SNIA standards. The "open" calls of the SSSI PCIe SSD Committee are designed to foster a broad understanding of technologies.  All SNIA and SSSI members, and those who are simply interested in technology advances, are welcome to attend.  Spread the word!

Join SSSI members for an “open” call on March 10, 2014 at 7:00 pm ET/4:00 pm PT.  SSSI member Jerome McFarland, Principal Product Marketer at Diablo Technologies, will talk about how memory channel storage technology works, how it’s deployed, and its advantages for applications.

Dial in at 1-866-439-4480 passcode 57236696.  A WebEx will be available at http://snia.webex.com, meeting number 792 152 928, password sssipcie.

The SSSI PCIe SSD Committee is a SSSI member committee that provides guidance to the marketplace on SSDs.  This can take the form of educational materials, best practices documents, and SNIA standards.

The “open” calls of the SSSI PCIe SSD Committee are designed to foster a broad understanding of technologies.  All SNIA and SSSI members, and those who are simply interested in technology advances, are welcome to attend.  Spread the word!

Why the FCoE – iSCSI Debate Continues

This is my first blog post for SNIA-ESF.  As a Principal Storage Architect, I have been doing extensive research on the factors that are driving FCoE vs. iSCSI choices over the last several years. The more I dive into the topic, the more intriguing the debate becomes. In fact, this blog is a preview of an upcoming white paper I’m writing and a Webcast SNIA is hosting on February 18^th. If you agree this debate is interesting, I encourage you to attend. Details on the Webcast are at the end of this post.

A Look Back at FCoE and iSCSI History

There are two entrenched standards for block storage protocols over Ethernet networks.  FCoE was ratified in 2009, while iSCSI was ratified in 2004.  Of course, various vendors and early adopters supported these protocols before ratification, so the history of these protocols is a couple of years longer than it looks, respectively.  While iSCSI simply encapsulates the SCSI protocol in IP, FCoE operates lower in the network stack and to do so required many enhancements to Ethernet.  While iSCSI runs on any IP network (mostly Ethernet these days), FCoE requires Data Center Bridging and Converged Network Adapters all running at 10 Gbps or faster.

All of the Data Center Bridging enhancements that make FCoE possible, like lossless Ethernet, benefit all of the protocols using Ethernet as the transport protocol.  DCB doesn’t just make FCoE possible, but it improves iSCSI at the same time  (see the SNIA-ESF blog, How DCB Makes iSCSI Better). So given that modern servers, networks, and storage may all be connected by hardware capable of running FCoE, that same network is also able to run iSCSI, as well as other network traffic.  Nothing precludes them from running simultaneously on the same network either.  The leading storage vendors that offer both FCoE and iSCSI target systems allow administrators to present the same LUN over either protocol with little effort, so a transition from one protocol to the other is not difficult.

Strengths and Weaknesses

So which network protocol is the right choice?

Each protocol has strengths and weaknesses when judged relative to each other.  FCoE has higher throughput at lower host CPU utilization than iSCSI and FCoE doesn’t have to process the TCP/IP stack as iSCSI does. iSCSI is relatively simple to setup and troubleshoot when compared to FCoE because zoning is not a factor and IP connectivity (although not optimized for storage traffic) is likely in place already.  Also, while FCoE has a comprehensive set of existing tools available to ease troubleshooting, there aren’t as many qualified people to use them in most enterprises.  Ease of use, plus the ability to use low cost NICs and switches, gives iSCSI a cost advantage.  (However, if you check out our SNIA-ESF webcast, “How VN2VN Will Help Accelerate Adoption of FCoE,” you’ll hear about new technologies that reduce the costs of deploying FCoE.) FC, and by extension FCoE, are perceived to be enterprise-grade, suitable for all workloads; and while iSCSI is being widely adopted at the enterprise level, it is still perceived by some not to be ready for Tier-1 applications.  The graph below is excerpted from the report “Intel 10GbE Adapter Performance Evaluation” prepared by Demartek for Intel in September 2010.  This data is consistent with the rest of the report findings and is only intended to be representative of the results from comparative iSCSI and FCoE testing.  The report is interesting reading and I recommend looking at it for more information. This graph shows IOPS and CPU utilization for JetStress tests running against NetApp storage over multi-path iSCSI and FCoE.  Note that latencies were all similar and running the tests against EMC storage showed similar results.

Many other factors must be considered, but according to industry pundits- as well as my own personal experience – in the majority of cases either protocol is adequate for the task at hand, and that is to effectively transfer block data across an Ethernet network.

Maximizing Throughput

The reality is, most servers, applications, and storage arrays simply won’t take advantage of FCoE’s superior performance or any storage protocol running over 10GbE.  iSCSI and NAS protocols are very fast and are typically sufficient to meet most application requirements.  But this is not meant to be a SAN vs NAS post – besides years of history, thousands of happy end users, and billions of continued investment show that both work well enough to meet most business needs.  The commonly deployed storage systems and hosts are simply not configured with enough hardware to saturate multiple 10 gigabit network links.  While this is rare today, it is going to become more common to see systems capable of saturating 10GbE pipes in the near future, especially as flash memory, either in all-flash arrays or tiered storage systems, find more application.  (Hear more on the impact of flash in our SNIA-ESF webcast, “Flash – Plan for the Disruption”). At least as it relates to spinning media disk systems – network bandwidth increases faster than storage system throughput can keep up.  So consider the storage system to be the bottleneck or limiting factor when evaluating storage network performance.  After all, in most data center environments, the ratio of servers and applications to storage systems is high. So, it’s reasonable to expect the storage system to be the bottleneck.  The absolute throughput of FCoE and iSCSI, when pushing a storage system to its limits, is not sufficient alone to be used as the sole basis for the decision between the two protocols except, for a few edge cases.  Bottom line: Whether the storage system is the bottleneck or the network is the bottleneck the performance relationship between FCoE and iSCSI does not change.

These edge cases tend to be extremely IO intensive database workloads and big data applications, such as Hadoop.  Citing the graph above, FCoE is about 15-20% faster on identical hardware than iSCSI.  Granted this is a single graph of a single test, but the data is consistent across tests performed by IBM using Emulex network interfaces.  If absolute throughput and efficiency (both network and CPU) are the only criteria when deciding between block protocols, FCoE looks like the choice.  Since these cases are rare – because complexity, supportability, and even politics are almost always considered – the decision is not so obvious.  Again, beyond the scope of this article, NAS protocols should be considered when determining the proper protocol for an application also.

Is There a Clear Winner?

While FCoE can claim technical superiority, iSCSI has the edge in cost and supportability.  The number and range of systems supporting iSCSI connectivity is greater, particularly at the entry level.  What’s more, the availability of people that can troubleshoot end-to-end connectivity for iSCSI is also much greater.  (The “ping” command diagnoses most iSCSI connectivity problems.)  Also, do a resume search on Monster or LinkedIn and the number of people that can configure VLANs dwarfs the number that can properly zone a Fibre Channel network.  Greater familiarity reduces the support and operating cost of iSCSI.

IDC predicts that FCoE revenue will ramp very quickly through 2016. (If available to you, see the IDC Worldwide Enterprise Storage Systems 2012-2016 Forecast Update.)  As customers decide to transition existing Fibre Channel networks to an Ethernet infrastructure, deploying FCoE would be a comfortable choice due to existing IT expertise and functional expectations of the Fibre Channel protocol.

Both iSCSI and FCoE are capable storage protocols and choosing one over the other will likely be dependent upon budget, IT skill set, and application requirements

Don’t forget to join us on Feb. 18^th

Again, I encourage you to attend our February 18^th Webcast, “Use Cases for iSCSI and FCoE –Where Each Makes Sense.”  Analysts from Dell’Oro Group will share their latest market research on this topic and I’ll dive into use cases for both iSCSI and FCoE. It’s a live event, so please come with your toughest questions. I hope you’ll join us!