iSCSI emerges as a viable SAN option

Posted on December 01, 2002

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Early adopters paint a picture of iSCSI as a capable technology for building low-cost SANs.

By Alan R. Earls

In the "religious wars" that have raged in recent years, iSCSI (or IP storage) has often been positioned as a panacea that will stretch familiar open systems technology around the model of Fibre Channel storage area networks (SANs) and make storage easy, cheap, and more manageable.

But doubters remain, and even devotees have fretted about the long wait for products and an approved standard. Recently, however, iSCSI has emerged from product brochures and analyst reports and has set down roots in at least a handful of respectable IT shops where reports on iSCSI's capabilities are upbeat—albeit not overly effusive. Indeed, user comments are reminiscent of what one might hear from an owner of a low-cost Toyota. With its non-sexy practicality, iSCSI delivers a good, no-frills data movement capability at an attractive price. It's not the hottest technology out there, but for some users and some situations it's exactly the right choice. What's more, "IP and SCSI have been around for 20 years so they are in everyone's comfort zone," says Michael Karp, an analyst at Enterprise Management Associates.

"We've done some benchmarks between Fibre Channel-attached storage and iSCSI-attached storage [without TCP/IP accelerator cards] and found only a slight degradation in performance on even our most demanding SQL servers," says Kevin King, an IT engineer at NRG Energy, a Minneapolis-based power producer that recently implemented iSCSI. "We have not seen any alarming performance issues, nor have our end users noticed any problems," adds King. However, he admits, there may be situations where some servers might push iSCSI harder and yield different results.

When NRG chose to implement iSCSI it had an extensive IP network in place. Thus, explains King, the most compelling reason for going with iSCSI was the ability to set up and manage the storage network using existing human and material resources.

NRG's initial storage infrastructure included two SAN islands. The first island was at the main data center, and the second was located across town at a disaster-recovery site. In an effort to simplify the storage network, NRG implemented Cisco 5428 storage router clusters to replace Brocade Fibre Channel switches and Cisco 5420 routers. "We then incorporated FalconStor's IPStor software to help manage and utilize our disk arrays more effectively, as well as provide block-level asynchronous replication between the two SAN islands," says King.


Figure 1: The Cancer Therapy and Research Center uses a pair of Cisco SN 5428 routers to consolidate servers at primary and backup data centers and to migrate data to Fibre Channel disk arrays at each site.
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The company is currently using both Cisco and FalconStor iSCSI client software. The primary iSCSI disk provisioning is done through the 5428 routers using the Cisco iSCSI client. Windows 2000 file servers, SQL servers, and Oracle servers also use the Cisco iSCSI clients, while FalconStor's iSCSI client operates on only one server—the one that publishes TimeMarks to the help desk, enabling administrators to create multiple, instantaneous point-in-time snapshot copies.

King says getting iSCSI systems up and running was fairly painless. For example, the install time for Cisco's storage routers was just minutes. "It was a very easy, straightforward implementation," says King.

Although iSCSI deployment went smoothly, King admits there were a few small problems. "There is no real magic to implementing iSCSI," he says, "but as a very early adopter of Cisco's iSCSI equipment we ran into a few minor issues with the routers and clients." However, King adds that Cisco was able to quickly resolve those issues.

Above all, King says iSCSI is no longer just an experiment. Looking ahead, he says NRG will continue to keep on top of the iSCSI environment as it changes and will probably continue to deploy further enhancements.

CTRC takes iSCSI plunge

Mike Luter, CTO at The Cancer Therapy and Research Center (CTRC), in San Antonio, TX, has also taken the iSCSI plunge. CTRC handles more than 10,000 patient visits each month and supports research and other activities. Luter explains that a primary goal of his iSCSI implementation was to ensure high availability—with no outages to exceed 10 minutes at any time. An IP network was already in place, linking CTRC's data centers at two campuses 22 miles apart and providing interconnection within those campuses. CTRC deployed a redundant pair of Cisco SN 5428 storage routers to consolidate servers at both the primary and backup data center and to migrate data to a Fibre Channel storage array at each site (see Figure 1).

CTRC is using Cisco's "Network Boot" feature to access servers both locally and remotely, directly from the network/storage array. This allows faster and simpler server deployment, as well as fail-over in case of server crashes. Luter says that iSCSI's ability to provide availability and its relatively low cost were keys to its adoption, a process that started about a year ago. And, he notes, booting to a fabric over iSCSI using the IP network was very cost-effective. "It gave us the ability to have a spare server at the primary or backup site and bring it right back up.

"We will eventually have 45 servers on our SAN—the high-availability, high-volume servers will be Fibre Channel-attached, and the low-volume servers will use iSCSI," he adds.

Overall, Luter gives iSCSI high marks. In fact, almost the only negative has been an increase (albeit only about 10 seconds) in the time required to boot.

Wireless Retail touts iSCSI

George Nathanson, director of IT at Wireless Retail Inc., in Scottsdale, AZ, expresses a similar degree of enthusiasm. "If I had an unlimited budget, would I have chosen iSCSI? Perhaps not; however, there are some processes that don't require anything more than a basic connection to the SAN, and for those, iSCSI is very cost-effective," he says.

Wireless Retail, which operates from more than 1,100 locations nationally, has network storage infrastructure at two different locations. The primary network, housed in a collocation facility, consists of about 20 application servers running primarily Windows 2000 and outfitted with standard Gigabit Ethernet network interface cards (NICs) for connectivity to the IP data network. The company expects to add more storage when it moves to a document imaging system to automate and manage contracts originating at point-of-sales kiosks.

In addition to facing up to its projected growth, Wireless Retail was finding that direct-attached storage was becoming increasingly difficult and costly to manage on an individual server basis. For example, the Exchange server had run out of space, forcing the IT department to repeatedly dump files to create space. However, the company had very little Fibre Channel expertise in-house and wanted to avoid the costs and complexity associated with implementing an all Fibre Channel-based SAN.


Figure 2: Wireless Retail's iSCSI SAN encompasses both IP and Fibre Channel protocols.
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Instead, Wireless Retail decided to go with a multi-protocol SAN approach using a combination of Cisco SN 5428 storage routers and a Fibre Channel disk array from pre-merger Compaq (see Figure 2). Instead of having to purchase Fibre Channel HBAs, the company simply had to download free Cisco iSCSI drivers and load them onto the servers to provide connectivity to the SN 5428s. Wireless Retail used the Fibre Channel ports on the SN 5428s to plug into the storage array, to which the iSCSI-enabled servers then had access.

Nathanson explains that Wireless Retail had grown dramatically in recent years, from four to more than 30 servers, with another 10 servers reserved for development work. "We found we could get more bang for the buck for storage with a SAN, but when our budget was cut we had to look for more inventive ways to implement the SAN," he says.

Nathanson says that iSCSI provided the right combination of capabilities at the right price to make the SAN a reality: "iSCSI was a natural fit because I can connect quite easily for relatively low cost."

While the three iSCSI implementations discussed so far have been for internally focused applications, at least one customer is putting iSCSI in the most visible place possible: as a frontline infrastructure available to customers.

InteleNet: iSCSI fit the bill

InteleNet, in Irvine, CA, a provider of outsourced data-center services, offers a range of hosting services—from Website hosting on dedicated servers, to complex application hosting of large e-commerce sites, to managed services and consulting.

Mark Towfig, president and CEO of InteleNet, explains that he had traditionally targeted larger enterprises but saw an opportunity to provide something similar for smaller companies at a lower price. iSCSI fit the bill.

The company is currently testing StoneFly Network's Storage Concentrator in its pre-production lab. The unit will be the cornerstone of the new service/product offering InteleNet plans to release in Q1 2003. The new product is a "self-service infrastructure" that will enable customers to go online and easily select and deploy servers, storage, and services as needed, or on-demand.


Note: Survey respondents included end users as well as systems integrators, value-added resellers, and OEM vendors.
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For example, InteleNet's service will enable users to select a Linux server, the amount of storage required, whether they want a firewall, as well as other features. Customers can use the Storage Concentrators running iSCSI to easily provision the storage space they need, when they need it.

"The heart of our infrastructure is the storage, and by deploying the Storage Concentrators we can have low-cost diskless machines sitting on racks, which allows the company to operate in a cost-effective and efficient manner," says Towfig.

"The iSCSI technology is very simple to understand and implement," Towfig reports. What's more, "iSCSI can be scaled as much as you want."

The attributes (e.g., scalability, familiarity, manageability, and low cost) that users frequently mention may bode well for iSCSI in coming months. Also, says Enterprise Management Associates' Karp, because iSCSI is built on Ethernet, which keeps increasing speeds by powers of 10, "100GbE will eventually be available for iSCSI."

Although equally sanguine about the prospects of iSCSI, Enterprise Storage Group analyst Arun Taneja warns that too much is being made of iSCSI's "familiarity." "The learning curve may not be as steep as with Fibre Channel," he says, "but there's plenty to learn and there will be new management tools needed to handle the special requirements of storage." That being said, Taneja adds that "[his] belief is that iSCSI will have a place, but that place will be more in departments or smaller, remote locations than in the data center."

Finally, Ahmad Zamer, chairman of the iSCSI subgroup of the Storage Networking Industry Association (SNIA), and a senior product line marketing engineer at the LAN Access Division of Intel, offers his perspective on the oft-quoted statement that iSCSI standards are late in coming: "Many people are under the mistaken impression that the standard is delayed, but compared to Fibre Channel at a similar point in its development it is actually ahead," says Zamer. He says that the standard-setting process used by the Internet Engineering Task Force (IETF) requires extensive, industry-wide interoperability demonstrations and mandates product availability.

Zamer contends that iSCSI interoperability demonstrations at the Storage Networking World conference in October were an important step and that the final draft specification is currently being reviewed—probably culminating in approval of a standard around February.

"We think end users are already putting a lot of trust in iSCSI, but of course they would like a finalized standard," says Zamer. "Once it comes out and they see that the industry can put together interoperable products, that will change the perspective of a lot of people."

Alan R. Earls is a freelance writer in Franklin, MA.


INTEGRATOR VIEW

iSCSI gives end users what they want
By Stephen Foskett

iSCSI will succeed because it is useful, inexpensive, and based on familiar technology (TCP/IP), but it does not spell doom for network-attached storage (NAS) and Fibre Channel.

The use of standards-based networking to transport block-level data is appealing on both a technical and business level. Many firms, afraid to take the plunge into the unfamiliar waters of Fibre Channel, are waiting for just such a standard before consolidating their storage on a network. However, as with any technology, the success of iSCSI will depend on a critical mass of hardware and software support, adequate pricing, and user acceptance.

While iSCSI hardware and software are just starting to hit the market, the outlook looks bright. Heavy hitters such as Adaptec, Cisco, IBM, and Intel have committed to the standard, and others, including Microsoft, are in for the long haul, too. Thanks to Cisco, software-based iSCSI implementations are available today, and they work fine. The first iSCSI hardware to appear in volume are "storage network interface cards (NICs)" with TCP offload engines (TOEs) and other storage-centric features. These cards are available from vendors such as Agilent, Alacritech, and Intel, with other vendors (such as Adaptec, Emulex, and QLogic) to follow. iSCSI translation boxes are also available, and iSCSI disk arrays will be coming soon.

Although not the bargain some envisioned, pricing for iSCSI hardware is at least competitive with comparable NAS and low-end Fibre Channel products. While iSCSI packets might occasionally flow over existing corporate networks (for migration or replication), it is likely that most iSCSI storage area networks (SANs) will use dedicated networks. The cost of Ethernet switches, IP routers, and TCP-enabled NICs will add up, but the total bill will probably not be more than the cost of low-end Fibre Channel switches and host bus adapters (HBAs).

User familiarity is another plus for iSCSI. Systems administrators are used to addressing storage at a block level, and companies have plenty of IP and LAN expertise on staff. The block-based nature of iSCSI is also appealing. While it is true that most server environments include a certain amount of file-based I/O, this is normally used for end-user access rather than centralized applications. Database administrators, too, are loath to using file-level access. Although the days when databases did not support NAS have passed, databases on NAS are not common.

The other side of user acceptance is the opinion of IT decision-makers. With management, iSCSI gets a free pass due to its association with Ethernet and IP. Relying on familiar technologies will reduce training requirements and ease staffing challenges. The assumption that costs will be lower due to iSCSI's use of Ethernet hardware may be less valid. However, perception is the important issue, and iSCSI can chalk up another win for user acceptance.

The greatest concern today is the lack of native iSCSI storage systems, which are necessary for the long-term success of iSCSI. NAS vendors could be big winners here since they could easily transform their products into iSCSI arrays.

iSCSI vs. Fibre Channel, NAS

Will iSCSI spell the end of Fibre Channel and file-based NAS? Absolutely not. The inherent latency issues of encapsulating channel data for transport across a general-purpose network will probably always stand in the way of ultimate performance. Also, although TCP overhead will be mitigated by offload engines, it will remain an impediment to performance. Dedicated channel I/O and network file servers are natural fits for certain tasks, and iSCSI should not be considered for those.

Although Fibre Channel has succeeded as a high-performance storage interconnect, carrying SCSI traffic between hosts and storage systems, this is not all it could have been used for. The fact that it rarely transports other payloads—like IP—is telling. Many of today's SANs are really just direct-attached storage channels with Fibre Channel switches in the path. The benefits of storage consolidation are lost when small SAN islands are not interconnected and storage is not shared. In the high-performance connectivity market, the greatest challenger to Fibre Channel will be InfiniBand, not iSCSI. InfiniBand looks like a sure thing for inter-host connectivity, and its performance and scalability should edge out Fibre Channel for fast direct-attached storage. If iSCSI takes over the market for low- to midrange SANs, Fibre Channel will be left to defend the high end of the SAN market against InfiniBand.

File-based NAS will also continue to be a necessary part of the IT landscape. Traditional NAS makes too much sense to be replaced, though the protocols will continue to evolve. However, iSCSI may put an end to the dream of using traditional NAS protocols for database storage.

The crystal ball

I predict that iSCSI will flourish in the low-end and midrange markets, and Fibre Channel will continue to dominate the top of the storage pyramid.

The future for iSCSI is particularly bright where cost and familiarity are more important than performance. It will open up a new market for consolidated SANs—one that is currently unserved. IP may become the dominant SAN choice of small companies. End-user surveys have indicated that firms of all sizes will implement both IP and Fibre Channel SANs, and most users think that iSCSI will find a place along with NAS and Fibre Channel.

Stephen Foskett is a senior consultant at GlassHouse Technologies (www.glasshousetech.com) a vendor-independent storage strategy and services firm in Framingham, MA.


Recent iSCSI product announcements

Joining Alacritech and Intel, Agilent Technologies next month will begin shipments of an adapter that offloads iSCSI and TCP/IP processing from host CPUs. The low-profile 1Gbps card is based on a full offload design and can be used in either initiator (host) or target (storage subsystem) mode for block (SAN) or file (NAS) I/O. The ANIC-2101A comes with a full-height bracket, while the ANIC-2103A has a half-height bracket. Both plug into a 32/64-bit, 33/66MHz PCI bus. OEM sample price is $850.

Until disk and tape subsystem suppliers ship devices with native iSCSI support, end users will have to rely on bridges to connect SCSI subsystems to Ethernet/IP networks via the iSCSI protocol. Two vendors are currently shipping iSCSI-IP bridges: Atto Technology and Okapi Software.

Atto's iPBridge 2500C supports both iSCSI and the Network Data Management Protocol (NDMP) 4.0. The 4U CompactPCI card is designed primarily for tape library vendors and comes with two Gigabit Ethernet and two Ultra160 SCSI ports. The bridge is priced at $4,495.

Okapi's ipXtensionCord remote tape appliance supports iSCSI and 10/100/1000 Ethernet. Priced at $995 and $2,495 for the 10/100 and Gigabit Ethernet versions, respectively, the appliance connects servers to SCSI tape drives and libraries over Ethernet, eliminating SCSI's distance limitations. The ipXtensionCord supports Linux iSCSI software drivers and Intel's PRO/1000 T IP Storage Adapter for Windows 2000/NT and Linux platforms.


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