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The first application of optical networking to benefit users * SAN and NAS primer * Key players * Key trends
January 23, 2001
22 Min Read
As traffic on the Internet continues to grow explosively and become more valuable in terms of the applications it supports, a big problem is emerging for many corporate users. Data storage is getting much more important, and much more difficult to manage.
Luckily, optical networking is coming to the rescue. Low-cost, high-speed connections are beginning to enable companies to build storage area networks (SANs) that serve multiple sites, rather than just a single data center. This centralization promises to deliver big benefits in flexibility and economy of scale.
And that’s just for starters. The idea of offering remote storage services – such as disk mirroring and disaster recovery – is catching on. A new breed of storage service providers (SSPs) is emerging, one that promises to extend the use of SANs to smaller companies as well as offering wholesale storage services to other players, such as application service providers (ASPs).
"Storage networking is exploding," says Johna Till Johnson, senior vice president and CTO at Greenwich Technology Partners, a consultancy. She says network storage is opening a new era in which whole data centers will function "on a cloud in the sky."The bottom line?
This is the first application of optical networking that delivers direct benefits to corporate users, the folk that are used to spending big bucks for their communication networks. That’s good news for them, and it’s also good news for carriers that are looking for ways of making money out of the optical infrastructure they’re installing.
From a service provider perspective, storage networks are also a no-brainer because the bandwidths required typically consume a whole wavelength. In other words, there’s no need to buy extra gear, such as edge switches, to pack lower bandwidth services into wavelengths – and that equates to less investment, less risk, and quicker revenue generation.
Some carriers are already jumping on the bandwagon. "We found that the leading demand for optical networking services is being driven by storage," says Jon Oltsik, vice president for marketing at GiantLoop Network Inc., a startup whose model includes DWDM (dense wavelength-division multiplexing), dark fiber, and managed services in a range of U.S. cities.
It’s important to realize that local storage networks are already commonplace in corporate data centers. "Large, unpredictable storage requirements have validated the move to create a distinct, dedicated network for stored information on the back end of the LAN," says Arun Taneja, director at The Enterprise Storage Group Inc. a consultancy. "Any company with large storage growth is putting together a storage network today."
The new thing is that their reach is being extended to multiple sites. “Storage networks are getting bigger, they're getting more widely networked, and optical's the way they're getting networked," says John McArthur, vice president for storage research at market research firm IDC.
All the same, storage networks themselves are quite complicated, and right now there are plenty of questions over which particular technology will win the day and which vendors are here to stay. The best way of minimizing risks and maximizing rewards is to do your homework -- get a grip on the basics and dig into the details.
Light Reading has taken the sweat out of this process in the following report. It outlines the basic principles involved, then delineates the key trends afoot. It also lists companies active in storage networking and points to nascent startups that might hold the key to future developments.
Follow the report sequentially, or click right to the part you want. Hyperlinks are as follows:
Storage Networking Basics
SAN vs. NAS?
Trends in Storage Networking
Storage Networking Glossary
Vendors: Brocade -- and Beyond
Other Useful Links
Next page: Storage Networking Basics
Storage networking has evolved to the point where a set of preferred topologies and techniques have been established. In this page and the next, we'll take a closer look at the basic elements that make up most storage networks today.
The diagram includes elements of the two key approaches to creating a storage network today -- SANs and NAS. SANs are storage-area networks, in which multiple database, Web, or file servers are attached to disk drives, usually via Fibre Channel switches and hubs. NAS is network-attached storage, in which specialized file servers are used to augment backup and data delivery of servers on the corporate LAN. The two approaches are often used together in networks, to meet a different set of interlocking requirements.
We'll deal with the specific pros and cons of both SAN and NAS later. First comes a look at how they fit into the overall landscape of storage networks.
Let's first examine the setup at customer headquarters. (This scenario also might exist in the service provider's central office or colocation hotel -- wherever the centerpoint of a multisite SAN is located.) Here, the SAN is clearly delineated from other parts of the network in a setup that mirrors a corporate LAN, in which switches are fed by hubs from multiple workgroups and data centers.
The centerpiece of the SAN is the storage director, an example of which is the ED-5000 from McData Corp. (Nasdaq: MCDT). Directors typically feature 32 or more ports, contain integral switch fabrics, and feature full redundancy of all internal parts. Their job is to act as the central point of access into the SAN.
Directors link to both LANs (local area networks) and WANs (wide area networks). On the LAN side, they link to servers equipped with Fibre Channel host adapters and to mainframes via channel interfaces like Escon or Ficon. They also link to NAS filers, such as the NetApp series from Network Appliance Inc. (Nasdaq: NTAP).
Filers, in general, are quick and dirty solutions: They meet immediate needs for faster file service and increased capacity quickly and easily -- just plug one into the Ethernet LAN and it's ready to go. Typically, NAS is treated by the SAN as part of the server farm.
Fibre Channel directors govern the flow of traffic between user hosts and Fibre Channel switches, which are smaller, less fancy versions of the director. The switches in turn tap into Fibre Channel hubs that aggregate connectivity for a series of storage devices. The goal is to create a fast, secure, and dedicated link between end users (local or remote) and the data on the disk or tape drives.
Fibre Channel hubs, incidentally, have all the drawbacks associated with hubs in Ethernet LANs: They are limited to sharing 1 Gbit/s of Fibre Channel bandwidth in an arbitrated loop configuration of up to 126 nodes or devices. On the upside, they're cheap and easy to add to a network, making scaleability less of a chore.
Now let's look at the WAN side of the SAN. Storage directors aren't usually equipped with WAN interfaces. While director vendors see the need to add ATM, DWDM, and Ethernet interfaces, it's more common to find a separate device handling the link between SAN and WAN. (That way, the costly, high-end director itself doesn't need to be upgraded or changed every time a new segment is added.) These devices are known as WAN/SAN gateways. They include established products like the UltraNet Director from CNT Networks and newer, so-called SAN transport routers like the Silverline series from Entrada Networks (Nasdaq: ESAN).
WAN/SAN gateways connect Fibre Channel switches and directors to WANs running IP (Internet protocol), gigabit Ethernet, TDM (time-division multiplexing), Sonet, and ATM (asynchronous transfer mode). They have router interfaces, and they also can be linked directly to DWDM gear.
NOTE: There's no reason that SAN switches and directors can't be linked directly to DWDM equipment without gateways. But in practical terms, since the gateway serves as a demarcation point to routers and IP networks, it's likely that they'll also be used to hook the SAN to the optical metro network as well. (More on that later.)
Next page: SAN Vs. NAS?
That storage networks support two distinct approaches to backup and data delivery has fostered the notion that NAS and SANs are oppositional tactics. In reality, they're being used together.
To see why, it's important to take a look at the basic technologies underlying both SANs and NAS -- and the benefits and drawbacks of both.
Let's take SANs first. Today, SANs mean Fibre Channel networking. Why? Several reasons. First off, Fibre Channel has had plenty of time to evolve as the most widespread option for linking storage arrays of disks or tape drives to host computers. Until recently, it was faster than other options: Fibre Channel today supports rates to 1 Gbit/s; a 10-Gbit/s version is being devised by the T11 subgroup of the National Committee for Information Technology Standards (NCITS).
Fibre Channel also has inherent benefits for data transfer. Since it uses frames or blocks to move information, it's good for rapidly moving large volumes of data in relatively small chunks, such as the data required for multiple online credit card verifications.
"Because Fibre Channel's frame based, it offers higher throughput due to lower packet-processing overhead," says Greenwich Technology's Johna Johnson. "Its credit based link-level and end-to-end flow control also help avoid network congestion without frame loss or buffer overflow."
And because Fibre Channel's a physical and data-link layer topology, it doesn't rely on a specific operating system or data format. That makes it a boon for backing up large data centers where mainframes, Unix servers, and other disparate types of hosts coexist.
NAS, in contrast, offers different benefits. Since most filers come with gigabit Ethernet links built in, they're ready to rumble on high-speed LANs, offering immediate relief for overburdened servers. The NAS approach, in which server and storage are linked directly, can make data management easier and more sophisticated. Also, NAS file-based orientation often makes it more suitable for applications like Web serving, in which large amounts of data must be downloaded in response to multiple individual requests.
On the downside, being part of a LAN means NAS filers must take on network-layer overhead. And in the case of Ethernet, frames may be lost or buffered as files are shunted from network to server or vice versa. Experts say this hinders NAS's scaleability and slows down data delivery for applications like credit-card verification.
Most gurus say it's not a question of SAN versus NAS, but instead of how both approaches can be woven into effective storage networks. NAS filers, for instance, can be used to aggregate mainframe or server files for delivery to Fibre Channel SANs.
Johna Johnson says many businesses will opt to interconnect SANs, devoted to database traffic and online transaction processing, with bays of NAS filers dedicated to Web traffic. "It's not a case of 'either/or' but 'both/and'," she says.
It may not be long before the basic definitions of SAN and NAS change fundamentally. SANs may not always be based on Fibre Channel, for example. Many proponents of 10-gigabit Ethernet think their topology is ideal for SANs. In addition, Fibre Channel and SCSI (small computer systems interface) are being improved upon and put over IP (see IP Storage Spec Shapes Up).
What's more, new kinds of devices are evolving that combine the features of SAN and NAS. Products from the likes of TrueSAN Networks Inc., for instance, promise to combine parallel processing with online switching. Another notable startup, Cereva Networks Inc., makes similar claims but says it's added carrier-scale features to serve the SSP market. For more on these developments, see these other articles in Light Reading:
Cereva
Startups Ready Big SAN Switches
Cereva Details Storage Switch
Next page: Trends in Storage Networking
1. THE OPTICAL CONNECTION
The future of storage networks is optical.
The key reason for this is that optical networking is a quick and easy solution to the distance and capacity limitations of today's SANs.
Let's take distance first. SCSI, the preferred method for linking computers to storage in data centers, extends just 25 meters. Fibre Channel and mainframe channels such as Escon and Ficon have a reach of about 10 kilometers -- and perhaps 20km with optimization and tweaking.
DWDM can exponentially lengthen SAN distances by transferring the Fibre Channel or mainframe channel onto a wavelength of light. Using 15xx-nanometer lasers, for instance, makers of DWDM systems can drive a Fibre Channel link to a minimum distance of about 100km without regeneration.
DWDM also can help bolster the capacity of a storage network, because it allows for more traffic to be added to a single fiber connection.
Since DWDM is primarily a physical-layer transport, makers of optical gear say there isn't much to do to forge the link. "It's really an issue of network design. There's no change to the signal involved. All we have to do basically is assure that the power levels are the same between the Fibre Channel and DWDM boxes by adding or subtracting attenuators," says Todd Bundy, director of business development at Adva AG Optical Networking (Neuer Markt: ADV). He says the Adva FSP system, which is also OEM'd by Cisco Systems Inc. (Nasdaq: CSCO), has been tested to handle native Escon and Fibre Channel traffic.
DWDM vendors also tout the concept that using their wares to interconnect SANs gives users the option to make changes in a SAN without changing the storage switches or devices. Again, the physical-layer nature of DWDM means that a new topology can be supported for a SAN just by swapping in a card. "It's efficient. You can link Fibre Channel to our product, then use gigabit Ethernet later if that's what you want," says Eugene Park, director of marketing at LuxN Inc..
The growth in SANs and their adaptability to DWDM has made the storage networking market a key target for optical vendors. "The two main drivers for LuxN are gigabit Ethernet and Fibre Channel," says Park. "We see a lot of growth in this area."
2. STORAGE SERVICES
The mating of DWDM with SANs, along with the rising popularity of storage networking in general, has led to a trend to outsource storage networks. This trend has two facets: So-called storage service providers (SSPs) are appearing that specialize in offering off-premises backup to ISPs (Internet service providers), ASPs (application service providers), and others requiring large amounts of storage to support ecommerce or Web-based business traffic.
Experts see enormous growth potential for SSPs. Analysts from Morgan Stanley Dean Witter, for example, estimate that the SSP market will grow to $15 billion by 2005 from $273 million in 2000. SSPs such as StorageNetworks Inc. (Nasdaq: STOR), the analysts say, are poised to reap the benefits of strong market demand.
Storage networking also is becoming a specialty of alternative metropolitan-area service providers whose services are based on optical networks. As noted earlier, GiantLoop Network Inc., an optical services startup, says storage networking generates the leading demand for its services.
"Business customers want backup, content distribution, and data mirroring over a network supporting Fibre Channel, gigabit Ethernet, and IP," says Jon Oltsik, GiantLoop vice president for marketing. He says his customers turn to GiantLoop specifically to get their SANs onto an optical infrastructure.
3. IP SANs
There are several reasons why folk are seeking to make IP a key protocol for SANs. First of all, a spec for Fibre Channel over IP would serve to beat the distance limitations of today's storage networks. Second, it could be cheaper and more practical for many companies lacking in Fibre Channel know-how to run IP SANs instead. As someone recently noted on a Light Reading message board: "IP SANs will be in hot demand in the enterprise due to the fact that most enterprise customers do not have the expertise in Fibre Channel to construct, deploy, and maintain an FC SAN. With IP, the talent to run it is in house." And that in turn will be a boost to service providers seeking to offer storage easily to new markets.
Those seeking to put SANs over IP have taken their cause to the The Internet Engineering Task Force (IETF) and are set to have a solid document this year (see IP Storage Spec Shapes Up). While several specs are knocking around, the chief solution seems to be to tunnel Fibre Channel traffic from storage switches and devices into an IP link.
Not everyone is convinced that putting SANs over IP will answer a present need. "When you ask the storage-over-IP folks what specific applications it will serve, why customers would want IP SANs, you get a deer-in-the-headlights look," says Giantloop's Oltsik.
Others say IP SANs aren't needed to solve distance problems right now. "Most SANs are within a small campus or metro area. That's where the growth is," says Dino Balafas, director of product marketing at Qlogic Corp. (Nasdaq: QLGC).
The potential value of IP SANs remains to be seen. Another messenger on Light Reading's boards had this to say: "Frankly, IP is nice to have in terms of overall cost and maturity of technology; but data is mission-critical for most companies and theyare not going to throw away their Fibre Channel infrastructure and start over with IP. Where you will see IP making inroads is small to mid-sized companies (ones that use NAS or Network Appliance technology today)."
Ultimately, IP SANs will have to pass the tests of practicality and performance in live networks. "In the end, storage over IP will happen, and it's a viable alternative," says Enterprise Storage Group editor Arun Taneja. "But really, do users care if data is delivered via Fibre Channel or IP?"
Next Page: Storage Networking Glossary
Arbitrated loop: A basic configuration of Fibre Channel networks in which up to 126 devices can share a single segment or loop, with one additional node left for linkage to a switch.
Escon: Mainframe channel devised by IBM that supports data rates of 200 Mbit/s over fiber. Depending on configuration, Escon can reach distances from about 3 to 10 kilometers, depending on fiber quality and product features.
FCIP:: Fibre Channel over IP. A proposal advanced by the IETF's IP Storage Working Group for mapping Fibre Channel traffic directly onto IP, in order to facilitate WAN connectivity for SANs. More information is available at http://www.ietf.org/internet-drafts/draft-ietf-ips-fcovertcpip-01.txt
Fibre Channel: A network technology that sets up block-oriented streams of data over fiber at rates to 1 Gbit/s and distances up to 500 meters over multimode fiber and 1 km over singlemode fiber. Fiber Channel networks can be configured in switched or redundant loop topologies. Standards are governed by the American National Standards Institute (ANSI) and groups that support it, including the National Committee for Information Technology Standards (NCITS -- formerly X3).
Ficon: Mainframe channel devised by IBM that supports data rates of 1 Gbit/s at distances from about 10 to 20 kilometers over fiber.
Host bus adapter: The card that fits into a computer, server, or mainframe that links it via Fibre Channel or SCSI to a storage device or storage network.
iSCSI: A proposal advanced by the IETF's IP Storage Working Group for mapping SCSI onto the TCP (transmission control protocol) in order to allow storage links to be extended greater distances over IP networks. For more detail, see http://www.ietf.org/internet-drafts/draft-ietf-ips-iscsi-03.txt
JBOD: Just a bunch of disks. Disk drives stacked together in a rack with a single attachment to a server or mainframe.
NAS: Network-attached storage. The setup in which a high-end server, typically a filer, is attached directly to the network that's making use of the backup, instead of to a separate SAN. SANs and NAS are often combined in today's storage networks.
RAID: Redundant Array of Inexpensive Disks. A technology in which data is stored in distributed fashion across multiple disk drives to achieve redundancy and improved data transfer rates.
SAN: Storage-area network. A network dedicated to providing and managing storage and backup for business or carrier networks. Because they're dedicated networks, SANs offer greater capacity and better performance than traditional storage and backup techniques, in which mainframes, servers, or other host computers are attached directly to disk and tape drives and managed via special software. Most SANs today are based on Fibre Channel switches and hubs, configured to occupy the "back end" portion of a network, behind the data center or server farm.
SCSI: Small computer systems interface ("Scuzzy"). A short-range (25 meters or less) protocol designed to link host computers with storage devices such as disk drives. Typically implemented over copper cabling, SCSI is the most widely used and the oldest method of connecting computers to storage devices. Its distance limitations and lack of support for fiber helped launch the migration to SANs.
Storage director: A switch designed to link elements of a SAN or NAS across multiple sites. Storage directors are meant to act as a kind of switch of switches and are typically provided by makers of Fibre Channel switches.
Next Page: Vendors: Brocade -- and Beyond
The title of this section refers to the 800-pound gorilla of the SAN market, Brocade Communications Systems Inc. (Nasdaq: BRCD). For years, Brocade has owned about 80 percent of the market for Fibre Channel switches of eight to 16 ports. (The company does not yet offer a storage director, but at press time sources said plans were underway for an announcement this year -- possibly within the next month.) That's about 60 percent of the entire SAN equipment market.
By all accounts, Brocade's position is well merited. The company was able to produce a switch that worked well and was priced right when others could not. With a lion's share of a market headed for triple-digit growth, Brocade's been enjoying its reign (see Brocade's Business Booms and Brocade Sews Up a Good Quarter).
But some would-be competitors say the behemoth of SANs has been enjoying its rule a bit too much. They accuse Brocade of resisting efforts to create SAN interoperability standards. In the spring of 2000, for instance, Brocade was absent from a key interoperability demo of the Fibre Channel Industry Association (FCIA), although it belongs to the group (see Fibre Channel Vendors Split On Standards).
"They'd join a standards group just so they'd know what was going on, then they'd get in there and resist any changes they felt would threaten Brocade's position," said one source, who asked not to be named. "You can't blame them, though. I'd do that too, in their shoes."
Then came the next wave -- the advent of optical networking and IP SANs. And it looks as though Brocade's taking a new tack. The company says it's focused on a future beyond Fibre Channel. "We see a multiprotocol future in SANs," says Jay Kidd, Brocade vice president for marketing. He says Brocade is at work on its strategy to address a market that will have to support IP, Ethernet, Infiniband, and Sonet.
The company's been the image of a team player in recent months, focusing on partnerships with optical vendors and SSPs (see Brocade, Adva Pass Interop Trials, Tunable Filters Go Solid State, Adva Demos SAN Interoperability, and Brocade, Sanrise Announce Partnership).
A key element in Brocade's strategy is an agreement with Cisco Systems Inc. (Nasdaq: CSCO), announced this past June, which calls for the two to develop IP connectivity for SANs in MANs and WANs. Brocade will help create a SAN interface for Cisco routers, and will work with Cisco to link up Cisco's DWDM gear with Brocade's switches. Jay Kidd hints that more will follow.
Brocade's changed its standards-body persona as well: It recently joined the The Internet Engineering Task Force (IETF)'s IP Storage Working Group, this time as a wholehearted participant. Sources say the company's made a signficant contribution to putting Fibre Channel on IP (see IP Storage Spec Shapes Up).
Like Scrooge on Christmas morning, Brocade seems to see that the tide has turned and that it can profit more readily by helping the flow of optical SANs than resisting. As the storage networking market expands, as growing demand indicates that it will, there will be room not only for big players like Brocade but for a range of startups as well.
Here is a sampling of leading vendors in each of the product categories of networked storage:
Makers of Optical Networking Platforms with Guaranteed SAN InterfacesAdva AG Optical Networking (Neuer Markt: ADV)
Nortel Networks Corp. (NYSE/Toronto: NT)
ONI Systems Inc. (Nasdaq: ONIS)
Sorrento Networks Corp. (Nasdaq: FIBR)
Makers of Fibre Channel Storage DirectorsInrange Technologies Corp. (Nasdaq: INRG)
McData Corp. (Nasdaq: MCDT)
QLogic Corp. (Nasdaq: QLGC)
Makers of Fibre Channel Switches and HubsBrocade Communications Systems Inc. (Nasdaq: BRCD)
EMC Corp. (NYSE: EMC)
Gadzoox Networks Inc. (Nasdaq: ZOOX)
Inrange Technologies Corp. (Nasdaq: INRG)
McData Corp. (Nasdaq: MCDT)
QLogic Corp. (Nasdaq: QLGC)
Vixel Corp. (Nasdaq: VIXL)
Makers of WAN/SAN GatewaysAdva AG Optical Networking (Neuer Markt: ADV)
Entrada Networks Inc. (Nasdaq: ESAN)
Lucent Technologies Inc. (NYSE: LU)
SAN Valley Systems Inc.
Makers of Storage Servers and NAS FilersEMC Corp. (NYSE: EMC)
Network Appliance Inc. (Nasdaq: NTAP)Makers of Fibre Channel Adapters
Emulex Corp. (Nasdaq: EMLX)Makers of Manageable Storage Appliances
EMC Corp. (NYSE: EMC)
Storage Computer Corp. (AMEX: SOS)
Yottayotta Networks Inc.
Storage Service Providers (SSPs)StorageNetworks Inc. (Nasdaq: STOR)
WorldStor Inc.
Storage Networking StartupsCereva Networks Inc. (carrier-level, parallel-processing storage servers)
Pirus Networks (SAN to IP connectivity)
StoneFly Networks Inc. (SAN and gigabit Ethernet infrastructure products)
StoreAge Networking Technologies Ltd. (storage appliances; backed by Cisco)
TrueSAN Networks Inc. (high-end, parallel-processing storage servers)Next Page: Other Useful Links
Storage-related Articles in Light ReadingIP Storage Spec Shapes Up
Cereva Details Storage Switch
Top 10 Trends
Brocade Sews Up a Good Quarter
Inrange IPO Heats Up
Brocade's Business Booms
SAN Surprise Jolts Market
Fibre Channel Vendors Split On Standards
Fibre Channel Spec To Stretch SANs
Storage Networking Standards OrganizationsAmerican National Standards Institute (ANSI). Leading standards body in the U.S.
The Internet Engineering Task Force (IETF). The group that governs Internet protocol standards now has a working group devoted to IP Storage Networking, which in turn is trying to standardize methods of putting SCSI and Fibre Channel over IP networks.
National Committee for Information Technology Standards (NCITS). This group used to be the X3 committee; it is charged with building specs on Fibre Channel and SCSI for delivery to ANSI.
Industry Groups and Professional OrganizationsFibre Channel Industry Association. An industry group dedicated to Fibre Channel.
Fibre Alliance. A consortium for partners and resellers of Fibre Channel gear from EMC Corp. (NYSE: EMC). Also a source of information about developments in the field.
Infiniband Trade Association. A group dedicated to promoting and improving on Intel's Infiniband I/O technology for servers.
The SCSI Trade Association. A trade group for manufacturers and users of the small computer systems interface for fast I/O.
Storage Networking Industry Association. Not-for-profit professional group that sponsors conferences, a technology center in Colorado Springs, and various efforts to promote standards.
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