There is considerable discussion in the trade press about the value of converging the data center LAN and SAN. The typical argument that is raised is that it is notably more efficient to run one network than it is to run two networks. That argument sounds very familiar. That is the same argument that was made as part of the justification for converging voice and data networks. So, one could conclude that since that argument worked for voice and data networks it will work for the LAN and SAN. While that may be a valid conclusion, it took several years before a converged voice and data network became mainstream. Will that be the case with the convergence of the LAN and SAN or is this situation different enough that adoption will occur more rapidly?
This month's discussion will focus on the convergence of the data center LAN and SAN. We will explore some fundamental issues such as why exactly would an IT organization want to converge their LAN and SAN and if they do, how should they best go about doing it?
As we saw with VoIP, converging related technologies can result in significant benefits, but can also present some significant challenges. What advise can you give to IT organizations that are trying to plan for the possible convergence of the LAN and the SAN in their data centers?
Customers should carefully characterize SAN/LAN consolidation and simplification opportunities as they consider technologies like FCoE, NAS, DAS and iSCSI all as potential viable approaches.
HP recommends customers start at the server edge where the real-world savings are most substantial and then extend the solution over time. An evolutionary approach reduces cost, complexity and risk in the near term while maintaining continuity of operations and maximizing investments over the long haul.
Gartner data point:
When considering FCoE to simplify the server rack, look first to server vendors for complete integrated solutions that include not just the FCoE components, but also cable management, and software that merges control of I/O virtualization in with application management.
Storage networks can be independently designed and tuned to address unique storage traffic patterns, giving storage network designers more freedom to manage network congestion compared to a completely shared network infrastructure.
This allows customers to remove expense and complexity, and improve network performance without impacting the installed LAN/SAN infrastructure or disrupting existing management practices.
The end result is reduced risk and management complexity in the short term with a solid foundation for transitioning from dedicated Fibre Channel–based networking to Ethernet-based networking over the long term.
Top of mind in LAN/SAN convergence is FCoE. In order to provide an open and converged alternative to traditional Fibre Channel, the key challenges of lossless and multi-hop must be solved in a practical, real-world sense. A key milestone will be the standardization of a suite of technologies that are broadly grouped together as Data Center Bridging in the IEEE. Quite simply, without the luxury of an upper-layer protocol compensating for packet loss with retransmission, the underlying network must transition from best-effort to now become truly lossless. However, even when this is practical, the management of LAN and SAN are not converged and new networking hardware is required.
Best practice would include:
• Avoid unnecessary expansion of existing FC infrastructure
• Evaluate solutions for openness, flexibility, and ability to integrate
• Trial first with selective proof-of-concept deployments
• Transition progressively and as-appropriate from pure FC to FCoE
However, many Enterprises are actively pursuing alternatives to the cost and complexity of FC/FCoE: iSCSI, NAS, and particularly ATA-over-Ethernet (AoE) are seen are genuine alternatives, delivering greater flexibility, easier scale-out, lower cost, and overall simplification. Ethernet-based SAN is an extremely effective method for sharing disk drives through a low latency network.
Keeping SAN/LAN convergence objectives – namely, reduced complexity and lower costs combined with improved performance, productivity and profitability -- in mind, our advice for convergence customers falls into three main areas:
Maintain Design Principles
Customers looking to converge their networks need to ensure their implementation does not denigrate critical aspects of their environments - it is *not* a converged network if you break one of your networks in order to accomplish convergence.
Review Convergence Teams
No question, LAN and SAN teams may be anything but converged as to their day-to-day operations and best practices. However, with guidance from IT management and clear operational policies, the “Law of Unintended Consequences” can be averted, and the benefits of convergence realized far sooner. Because team transition takes far longer than infrastructure transition, customers are urged to review their IT personnel and perspectives with due diligence.
Select Convergence Platform
Storage- admins have long thought they can meet rigorous storage requirements only with FC switches, but new director-class Multiprotocol Ethernet Storage switches not only provide more flexibility&scalability than FC alternatives, their reliability is without parallel. Instead of force-fitting a specific box that may be inappropriate for their converged design, it's important to use the correct platform for the job.
The adoption of 10GBE opens the door for LAN-SAN convergence. Converged LAN-SAN takes advantage of the price/performance curve of Ethernet. The open and interoperable nature of Ethernet also provides an opportunity to deploy best-of-breed solutions without the proprietary nature (and vendor lock-in) associated with other SAN technologies. A converged Ethernet fabric can drive costs down significantly –cost of adapters, switches, cabling, along with the simplicity associated with a single fabric.
A few items should be considered before adopting a converged LAN-SAN. The performance of storage traffic on an Ethernet fabric needs to be ensured in the presence of bursty data traffic. With 10/40GbE, Data Center Bridging (DCB) technology can be deployed for predictability. For 1GbE, techniques like CLEAR-Flow can automatically detect, prioritize, and ensure bandwidth guarantees for storage traffic facing congestion.
Additionally, traditional architectures with multiple network tiers need to flatten to one or two tiers. Each tier typically adds latency and oversubscription, which can lead to poor performance for storage traffic.
Finally, departmental silos need to be overcome as a converged LAN-SAN fabric involves greater cooperation between network and storage admins, along with the increased usage of common tools and best practices, from both the LAN and SAN worlds.