构建面向未来的数据基础设施

Posts Tagged 'Virtual LANs'

  • March 02, 2018

    Connecting Shared Storage – iSCSI or Fibre Channel

    By Todd Owens, Field Marketing Director, Marvell

    One of the questions we get quite often is which protocol is best for connecting servers to shared storage?

    What customers need to do is look at the reality of what they need from a shared storage environment and make a decision based on cost, performance and manageability.

      list of Hewlett Packard Enterprise (HPE) component pricesNotes: 1. Optical transceiver needed at both adapter and switch ports for 10GbE networks. Thus cost/port is two times the transceiver cost 2. FC switch pricing includes full featured management software and licenses 3. FC Host Bus Adapters (HBAs) ship with transceivers, thus only one additional transceiver is needed for the switch port 

    So if we do the math, the cost per port looks like this: 

    10GbE iSCSI with SFP+ Optics = $437+$2,734+$300 = $3,471 

    10GbE iSCSI with 3 meter Direct Attach Cable (DAC) =$437+$269+300 = $1,006 

    16GFC with SFP+ Optics = $773 + $405 + $1,400 = $2,578 

    Note, in my example, I chose 3 meter cable length, but even if you choose shorter or longer cables (HPE supports from 0.65 to 7 meter cable lengths), this is still the lowest cost connection option. Surprisingly, the cost of the 10GbE optics makes the iSCSI solution with optical connections the most expensive configuration.

    It really comes down to distance and the number of connections required. The DAC cables can only span up to 7 meters or so. That means customers have only limited reach within or across racks. If customers have multiple racks or distance requirements of more than 7 meters, FC becomes the more attractive option, from a cost perspective.

    • Latency is an order of magnitude lower for FC compared to iSCSI. Latency of Brocade Gen 5 (16Gb) FC switching (using cut-through switch architecture) is in the 700 nanoseconds range and for 10GbE it is in the range of 5 to 50 microseconds. The impact of latency gets compounded with iSCSI should the user implement 10GBASE-T connections in the iSCSI adapters. This adds another significant hit to the latency equation for iSCSI.

    图 1: Cavium’s iSCSI Hardware Offload IOPS Performance  

    图 2:

    Keep in mind, Ethernet network management hasn’t really changed much. Network administrators create virtual LANs (vLANs) to separate network traffic and reduce congestion. These network administrators have a variety of tools and processes that allow them to monitor network traffic, run diagnostics and make changes on the fly when congestion starts to impact application performance.

    On the FC side, companies like Cavium and HPE have made significant improvements on the software side of things to simplify SAN deployment, orchestration and management. Technologies like fabric-assigned port worldwide name (FA-WWN) from Cavium and Brocade enable the SAN administrator to configure the SAN without having HBAs available and allow a failed server to be replaced without having to reconfigure the SAN fabric. Cavium and Brocade have also teamed up to improve the FC SAN diagnostics capability with Gen 5 (16Gb) Fibre Channel fabrics by implementing features such as Brocade ClearLink™ diagnostics, Fibre Chanel Ping (FC ping) and Fibre Channel traceroute (FC traceroute), link cable beacon (LCB) technology and more. HPE’s Smart SAN for HPE 3PAR provides the storage administrator the ability to zone the fabric and map the servers and LUNs to an HPE 3PAR StoreServ array from the HPE 3PAR StoreServ management console. 

    In many enterprise environments, there are typically dozens of network administrators. In those same environments, there may be less than a handful of “SAN” administrators. Yes, there are lots of LAN connected devices that need to be managed and monitored, but so few for SAN connected devices.

    Well, it depends. If application performance is the biggest criteria, it’s hard to beat the combination of bandwidth, IOPS and latency of the 16GFC SAN. If compatibility and commonality with existing infrastructures is a critical requirement, 10GbE iSCSI is a good option (assuming the 10GbE infrastructure exists in the first place). If security is a key concern, FC is the best choice. When is the last time you heard of a FC network being hacked into?

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