Brocade and Dell Enhance iSCSI Storage

Since the introduction of iSCSI storage in 2004, the population of 1Gb iSCSI storage arrays has grown to comprise almost a third of all disk arrays shipped each year. Connecting servers to all those 1Gb iSCSI SANs requires only a generic port on a server LOM chip, or 1GbE NIC. No special Ethernet hardware or software is needed because IP networks don’t discriminate between NAS/SAN storage traffic and LAN traffic. That’s because the iSCSI protocol is transparently encapsulated into Ethernet packets and only basic iSCSI-related network services exist.

In 2010, the general availability of 10Gb iSCSI storage positioned iSCSI as the leading performance technology for data center SANs. IT Brand Pulse expects Ethernet-based NAS, iSCSI and FCoE storage to extend that leadership. Beginning in the 2012 timeframe, the next generation of 16Gb Fibre Channel SANs will be generally available while the performance of NAS, FCoE SANs and iSCSI SANs will begin the migration to 40Gb technology.

After six years of limited adoption, the deployment of 10Gb Ethernet took off in 2010 as server virtualization emerged as the killer app. IT professionals are heavily loading servers with virtual machines and applications, which is driving the need for higher performance LAN and SAN connectivity. Data center managers are eliminating the potential I/O bottleneck by deploying the latest generation of 10GbE switches and CNAs to solve their performance problem today, and to provide a platform for converged networks in the future.

Brocade and Dell are planning to use 10GbE with Data Center Bridging (DCB) as a platform to deliver enterprise-class iSCSI storage for large data centers. Their new generation of iSCSI SANs include network connectivity with 10x more throughput than 1Gb iSCSI storage, and 25% more throughput than 8Gb Fibre Channel storage. In addition, their new 10Gb iSCSI SANs use innovative implementations of the suite of new protocols that comprise DCB. Their unique implementation allows data center managers to converge NAS, SAN and LAN traffic onto one Ethernet port, while providing granular control of separate QOS, and other network policies, for each type of traffic.

While 10Gb iSCSI has emerged as the fastest SAN technology, server I/O testing in real world environments performed by IT Brand Pulse validates that Brocade CNAs have emerged as the best performing 10Gb iSCSI adapter. At larger block sizes (128KB) the Brocade 1020 CNA demonstrated a slight performance advantage but extended their advantage over the other products tested at small transfers, being most prominent at 4KB with 330,620 IOPS. This represents a 34% greater number of IOPS than the nearest competitor.

Brocade and Dell are also helping data center managers migrate their established practice of standardizing on of 1GbE adapter and driver images. To efficiently deploy and manage server connectivity to LANs and iSCSI SANs, it’s very common for data center managers to standardize on a single 1GbE adapter and driver image. It’s then easier to maintain one type of spare hardware; become familiar with a single type of driver and management software; and to troubleshoot problems. In a survey conducted by IT Brand Pulse, 66% of the IT professionals that responded said that at least half of their servers used a standard NIC and driver image. Only 10% of the respondents said each of their servers uses a custom driver configuration. Brocade CNAs offer broad operating system support, including Windows Server 2003, Windows Server 2008, SuSE Linux, Red Hat Linux and VMware. The result is data center managers who are planning to migrate their LAN or iSCSI SAN to 10GbE, can also plan on standardizing on one 10GbE CNA across multiple operating environments.

A next logical step for server admins who deploy CNAs to provide 10GbE bandwidth to their virtualized servers, is to exploit the converged networking capabilities of the CNAs. When used for converged networking, CNAs can eliminate the cost and complexity of additional NICs, iSCSI HBAs, Fibre Channel HBAs and their associated cabling.

Brocade and Dell offer a broad range of products that support network convergence on Ethernet. The two companies also collaborated to shape two DCB protocols, Priority Flow Control and Enhanced Transmission Selection into tools for granular control of 10GbE and for optimizing the performance of a converged LAN / iSCSI SAN.

Originally developed to support Fibre Channel over Ethernet (FCoE) so that no frames would be dropped, PFC extends the granularity of PAUSE to accommodate different priority classes. Using PFC, a lossless lane for FCoE traffic can be created while retaining packet-drop congestion management for IP traffic. The result is SAN traffic can share the same link as LAN and IPC traffic.

ETS is used to assign traffic to specific lanes using class of service (CoS) values to identify which lane the traffic belongs to. PFC and ETS together allow administrators to allocate buffers, queues and other resources based on the priority of the application. The result is a predictable, high level of service for business-critical traffic.

CoS values are transmitted and discovered using the Link Layer Discovery Protocol (LLDP), and data for the different types of traffic are formatted as Type-Length Values (TLVs). Until recently, administrators could not separate LAN and iSCSI SAN traffic simply because support for iSCSI TLVs were not incorporated into most DCB implementations. Brocade and Dell are the first to provide an end-to-end 10Gb iSCSI SAN that takes full advantage of PFC and ETS.

Based on what I’ve learned about these products from Brocade and Dell, my recommendations are: a) If you’re purchasing a 10GbE server, networking or storage product, make sure it incorporates DCB to ensure interoperability with other products in the future; and b) If you’re planning to deploy a converged LAN / iSCSI SAN, ask your vendor if they have TLVs for iSCSI. You’ll want this to implement separate iSCSI and LAN Quality of Service using PFC and ETS.

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posted by: Frank Berry

Frank Berry, InfoStor Guest Blogger
by Frank Berry
InfoStor Guest Blogger

Frank Berry is CEO and senior analyst, unified networking practice, at IT Brand Pulse. He is a 30-year veteran of the IT industry, and has held senior executive positions at storage vendors such as QLogic and Quantum.