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Strengthen DR Through Intelligent Design

By mdetrick posted 11-05-2014 08:00 AM


Brocade 7840 Extension Switch


The Brocade 7840 is the most technologically advanced extension product on the market.  Brocade continues further innovation in extension with the introduction of the Brocade 7840 Extension Switch.  As a reminder, Brocade has originally developed nearly every significant aspect of extension technology since there has been extension.  Here is the current list of Brocade extension firsts:


  • Extension Hot Code Load (tunnels remain active during firmware upgrade)
  • Extension Trunking
  • FCR (Fibre Channel Routing)
  • Fabric Vision, Flow Vision and MAPS (Monitoring Alerting Policy Suite)
  • 40GE Interfaces
  • 10GE Interfaces
  • FICON Acceleration
  • FastWrite
  • OSTP (Open Systems Tape Pipelining)
  • ARL (Adaptive Rate Limiting)
  • IPsec for FCIP
  • PTQ (PerPriority-TCP-QoS)
  • WAN Optimized TCP (Head of Line Blocking elimination with “Streams”)

Enterprises today need to keep up with the explosion of data and still meet tight RPO and RTO requirements. The ramifications and potential business impact of an unreliable disaster recovery infrastructure are greater than ever.  Brocade understands these challenges and is the leader in extending storage fabrics over long distance to meet these requirements. With combined enterprise-class availability and Brocade’s innovative features, businesses can achieve always-on operations and maximize application uptime.

Cisco just released their latest extension product (MDS 9250i) with no new or innovative development. It’s a multi-protocol “Swiss Army knife” that’s not particularly good at its primary function: storage extension over distance.


So, why did Brocade invest in new innovative extension technology?  Clearly, extension is not going away and sales have never been stronger.  Extension architectures are growing and the applications are becoming more robust.  Brocade’s core competency is storage networking including extension. This blog highlights Brocade’s vast technology differences and benefits.  As the innovator holding many patents, Brocade’s technology makes extension a primary focus.


The result of our investment in extension innovation is the Brocade 7840; an enterprise-class product with the features and functionality required for disaster recovery solutions today and into the future.  The 9250i certainly doesn’t address the needs of most large enterprises.  Let me step through all the differentiation that that separates the Brocade 7840 from the Cisco 9250i.


The Brocade 7840 introduces the industry’s first 40 GbE interfaces for FCIP. Think it’s more than you need today? Here’s some background on why we built a future-ready platform with a look back on the Brocade FX8-24 blade.  When we were spec’ing out the blade, about 8 years ago, we surveyed our customers to see how many had 10 Gbps links or existing infrastructure, there were only two.  Nonetheless, Brocade moved forward with 10 GbE on the FX blade.  Today, it is rare to find enterprise customers that don’t have 10 Gbps links.  Many FX8-24 blade early adopters have upgraded enabling their 10 GbE interfaces without platform replacement.  Not only does the FX blade have 10 GbE interfaces, the engines behind them operate at near 10 Gbps.  Competing FCIP products with 10 GbE interfaces such as the 9250i do not operate anywhere near 10 Gbps line rate.  Do not be fooled!  Just because there are 10GbE interfaces on the front doesn’t mean it runs at 10 Gbps.  On the 9250i, you’ll be lucky to get half that.  The Brocade 7840 on the other hand has two 20 Gbps engines and can fill a 40 Gbps pipe.  Trust me, those pipes are coming.  Brocade already has customers using 4x 10 Gbps links, so, the natural progression is to move to 40 Gbps pipes in the coming years.  The Brocade 7840 can support legacy GbE, current 10 GbE, and future 40 GbE links.


Customers have indicated that one of the most important new features on the 7840 is the industry’s only non-disruptive firmware upgrades for extension with Extension HCL.  This is the ability to perform Host Code Load (HCL) with no disruption to FCIP connections.  This is a major technology achievement.  Brocade builds storage networking products to satisfy the highest standards of IBM System z.  Extension HCL is lossless and guarantees in-order delivery.  There will be no Interface Control Checks (IFCC) with Extension HCL.  This is patented technology created by Brocade engineering. The Cisco MDS 9250i is not capable of doing Extension HCL.


Extension Trunking is unique to Brocade.  Don’t confuse this with Cisco Port Channels because Extension Trunking is not a hash of a flow to a specific link like Cisco Port Channels. With Cisco Port Channels, if you have a flow sent to a specific link, you do not have bandwidth aggregation because the most that flow will see is that link’s bandwidth.  Also, you do not get granular load balancing because flows are not all equal and the hash doesn’t account for that.  If Cisco Port Channels are not Brocade Extension Trunking, what is Brocade Extension Trunking?  Extension Trunking is:


  • True bandwidth aggregation
  • Granular load balancing (batch based)
  • Failover/Failback
  • Lossless Link Loss (LLL)
  • In-Order delivery
  • Logically a single ISL
  • Backup circuit metrics
  • Failover groups

Extension Trunking was developed for the high standards of the mainframe and to prevent IFCC in the event that a circuit and its inflight data are lost.  Extension Trunking is very helpful and a key technology in most all extension architectures and use cases including open systems. 


For customers that need less bandwidth, but have a large number of sites, the Brocade 7840 has you covered.  The Brocade 7840 accommodates up to 20 sites at 2 Gbps each.  Of course, the number of sites vs. bandwidth can include everything in-between, i.e., 10 sites at 4 Gbps each….  The Brocade 7840 beats the competition in scale from small to large.  Licensing permits a cost effective entry level model with less bandwidth and by adding upgrade licenses can scale up to the largest enterprise use case.  This is prudent for most customers.


The new Brocade 7840 supports 9216 byte jumbo frames and fills the datagrams to their full MTU for optimal efficiency.  Additionally, PMTU is available to automatically determine the network’s MTU in the event the Storage Administrators can’t get that information. 

Brocade uses batches and there is only one FCIP header per batch of 16 FC frames.  This is a huge overhead savings!  Batches are compressed and transformed into a byte stream before being processed.  Jumbo frames permits larger byte streams to be transported which may be multiple batches per datagram.  This is incredibly efficient.  Recent customer tests of tape over metro dark fiber (60 km) demonstrated that their tape systems ran at more than twice the speed with the 7840 compared to without it (no compression because the tape was already compressed).  The 7840 provides a much more efficient transport for FC than FC itself can achieve.


The Brocade 7840 has all new hardware and software compression engines.  Brocade developed its own hardware-based compression for ultrafast throughput and ultralow latency, called Fast Deflate.  It is this mode of compression that would be used with synchronous applications.  Yes, the Brocade 7840 is appropriate for synchronous with 45 microseconds through the box.  The throughput as seen by the application side (FC/FICON side) is 40 Gbps per data processor, or 80 Gbps per 7840.  The Brocade 7840 can process more than 6x the data rates compared with Cisco MDS 9250i.  There are two other compression algorithms with higher compression ratios at the cost of lower compression rate, called Deflate (16/32 Gbps DP/Box) and Aggressive Deflate (10/20 Gbps DP/Box).  Even at these lower rates and higher ratios, the competition can’t come close.


WAN Optimized TCP (WO-TCP) is a new Brocade-developed TCP stack that replaced Storage Optimized TCP (SO-TCP).  WO-TCP is an aggressive, high-throughput, fast to recover TCP stack that implements “streams”, a TCP virtual windowing technology that allows an Initiator Target LUN Nexus (ITLN) to be treated autonomously across the IP network.  With traditional TCP, if multiple flows traverse a single TCP session and one of those flows were to slow or stop, that would cause all the flows to slow or stop.  With streams, all flows have their own autonomous virtual windows and no one stream can cause negative effects on another. 

WO-TCP was designed to fully utilize a link from Los Angeles to Hong-Kong (160 ms RTT) without droop.  WO-TCP has a large Bandwidth Delay Product (BDP) which means a large amount of data can be inflight before running out of TCP window space.  WO-TCP is in addition to PerPriority-TCP-QoS (PTQ). 


PTQ offers a separate WO-TCP session for each QoS priority.  It makes no sense to either run different priorities over the same FCIP/TCP session or to separate out priorities into different VE_Ports sacrificing the benefits of extension trunking.  With PTQ, extension trunking can be used (single VE_Port) with QoS and each TCP session can be individually marked with DSCP or 802.1P for transport across the IP network. 


The Brocade 7840 has Ethernet Interface Sharing which permits any circuit to be assigned to an Ethernet interface for the convenience of connectivity.  Ethernet interfaces are not fastened to specific VE_Ports or DP (Data Processors).  This is not true on competing products and the use of Ethernet interfaces and connections to data center switches/routers is often not optimal.

IPsec on Brocade Extension has been designed and is offered such that there should be no reason to not use it.  Here is why:


  • No additional license or cost (included in base unit)
  • Only 5 microseconds of added latency (hardware implementation)
  • Operates at line rate (20 Gbps on each DP)
  • Simple configuration (PSK on each side)
  • Supports all configurations
  • Supports Extension HCL (non-disruptive firmware upgrades)

So, really…  You are going to let data leave your physical data center unprotected?  No excuse! The Cisco 9250i has IPsec, but the performance suffers a performance penalty of at least 30% in application throughput when it’s enabled. Whereas the 7840 with IPsec enabled encrypts data flows over distance at full line rate without a performance penalty.


In addition to performance and availability capabilities, Brocade is committed to developing functionality that simplifies operations.  Paramount to this goal is the ability to get support issues resolved fast.  For example, when an extension related support ticket is opened, the first thing that has to happen is to figure out the root cause of a complex problem.  It can be in one or more of the following places: array (assuming RDR) or tape, local fabric (if fabric attached), extension box, local IP network, service provider, remote IP network, remote extension box, remote fabric, and remote array or tape. These support issues take longer to close because it can take a long time to sort through all the potential causes.  Brocade is focused on developing tools and technology to isolate and identify problems throughout the storage network infrastructure.  With these capabilities, problem diagnosis and resolution are swift. 


For example, we introduced Wtool; a new extension test tool that permits extension trunks (multiple circuits form a single tunnel, known as a trunk) to remain online while circuits are taken offline for test.  As long as at least one circuit remains in production the VE_Ports will continue to communicate.  Clearly, you want to keep tunnels up while testing a suspected circuit.  Taking an entire tunnel/trunk down to perform tests is disruptive and nobody wants that.  These are tools exclusive to Brocade and not available in competitive offerings.  Please refer to the Tech Brief on Fabric Vision for Extension.


That’s a long list of technology that’s unique to Brocade. These capabilities drive real value for extension customers through unmatched performance, reliability, and simplicity.  Get more for your money!  Buy a product that demonstrates true engineering prowess and is the culmination of superior innovation to meet and maintain your DR goals.  Check out the new Brocade 7840 and you will see the true difference.


Mark S. Detrick

Extension Principal Architect