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Understanding NAS interconnects: Fast Ethernet and Gigabit Ethernet

Storage managers use NAS interconnects are used to integrate NAS devices into their networks. Understanding NAS interconnects can help storage administrators make better decisions about how to deploy

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their NAS systems.

The best-documented NAS interconnect for connecting is Fast Ethernet, (FastE, 100 Mbps). While FastE is low-priced and easy to understand, it is slow for all but the most basic file-level chores. FastE is adequate for workgroups of 10 or fewer people transferring documents under 10MB in size. Once you get to larger documents, you'll reach the limits of FastE and will want to upgrade to the next level of interconnect: Gigabit Ethernet (1000 Mbps).

GigE is suited for a wider range of NAS interconnect tasks. With GigE, you can service a surprisingly large group of people transferring 10.1 MB files and larger. Even 100 people accessing the server at FastE speeds will see reasonable performance.

However, GigE will start feeling sluggish when you're servicing groups of 500 people, transferring a large mix of large and small files. You'll also see only workable performance when you start using protocols that offer block-level access to your NAS devices.

For these situations, our friends in the Ethernet networking world have come up with 10 GigE (10,000 Mbps). The newest member of the Ethernet family, 10 GigE is by far the fastest and can offer serious performance for even the most demanding of file environments. Most makers of enterprise NAS devices offer a choice of mix-and-match Ethernet connections. Price is usually the governing factor in choosing your interconnects. Generally speaking, the more expensive the device, the more exotic the interconnects are.

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Fibre Channel connections are normally reserved for SAN devices, but NAS vendors have started including Fibre Channel as well. Fibre Channel interconnects are offered in speeds of 2 Gbps, 4 Gbps and 8 Gbps. Fibre Channel encompasses both a protocol and an interconnect. As most enterprise SAN solutions cannot offer file sharing, NAS vendors offer ways for you to attach your NAS to your SAN using Fibre Channel. This allows you to open the storage you have in your SAN to file-level access through your SAN.

NAS devices also use Fibre Channel to offer low-latency, high-bandwidth block-level connections to multiple hosts. Fibre Channel has a leg up on GigE when it comes to bandwidth and latency, but competes on an arguably even performance playing field with 10 GigE. For those who want to leverage their investment in Fibre Channel, this interconnect offers the most value. A word of caution: Not all NAS vendors support Fibre Channel, and should you have it installed in your environment, you'll want to make compatibility a part of your RFP.

The newest interconnect for NAS devices is InfiniBand, a super-high-bandwidth, super-low-latency interconnect often used for high-performance computing clusters. InfiniBand started at around 10 Gbps and rumor has it 40 Gbps will be coming to market soon. (Just typing 40 Gbps brings a smile to this network administrator's face.)

With InfiniBand, we are talking about some extremely high bandwidth, with the ability to transmit a full-length, DVD-quality movie in three seconds. These interconnects are currently offered by only a handful of NAS vendors and are relegated to demanding environments, one of which I wish were my basement lab! InfiniBand has had a slow start as an interconnect. But as virtualization, at both the host level and storage level, gains steam in large-scale, non-mainframe systems, you'll see demand for such high-performance interconnects become more mainstream.

About the author: Tory Skyers is a senior systems engineer for Prudential Fox & Roach Realtors, an independently owned and operated member of The Prudential Real Estate Affiliates Inc. He frequently speaks at conferences such as Storage Decisions and also contributes regularly to SearchStorage.com's blog called Storage Soup.

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This was first published in April 2008

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