分类： 服务器与存储
2007-06-19 17:59:14
iSCSI is now supported on virtually all operating systems, and larger enterprises are using IP SANs in a wide variety of application environments.
Until recently, iSCSI was generally deployed only in small to medium-sized businesses (SMBs) running Windows applications. Enterprises that required the high performance and rich features of Fibre Channel rarely considered iSCSI as a viable alternative. Now, many enterprises that deployed iSCSI for second-tier Windows applications have become comfortable with iSCSI and are extending use of the technology to mission-critical applications. In addition, Microsoft’s support of iSCSI has pressured vendors of other operating systems, including Linux, Unix, and VMware, to follow suit.
A shift in attitude
iSCSI is a networking protocol that allows the use of SCSI over TCP/IP networks. It uses Ethernet, which is ubiquitous in both SMBs and large enterprises.
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According to Robert Gray, research vice president of storage systems for International Data Corp. (IDC), a user-perception shift has taken place regarding iSCSI. “Most buyers now think that iSCSI is mature and it works. They’re comfortable with the technology and consider it ready for production environments, with little to no risk,” says Gray.
Peripheral Concepts, another market research firm, recently conducted an in-depth end-user survey and found that 37% of respondents have implemented an iSCSI SAN, compared to less than 20% a year ago. Farid Neema, president of Peripheral Concepts, says that iSCSI has penetrated all business tiers, challenging the belief that iSCSI would be attractive only to small and medium-sized sites (see “iSCSI breaks through all market tiers,” p. 30).
Dr. Boris Anderer, CEO of Reldata, which sells IP storage virtualization gateways and software, believes there are three main factors driving iSCSI acceptance: expansion of iSCSI initiators, increased speed, and quality of service (QoS).
Initiators are software or hardware that pair network interface drivers and SCSI drivers. In addition to Windows, software-based initiators are now available for Linux, NetWare, VMware, AIX, HP-UX, Solaris, and other Unix varients. Several hardware-based initiators on host bus adapters (HBAs) and TCP/IP-iSCSI accelerator cards are available to boost performance in I/O-intensive environments.
“IP SANs are achieving transaction speeds closer to Fibre Channel,” says Anderer. “Many people don’t realize that it’s common for high-performance IP SANs to trunk two to four 1Gbps iSCSI lines together to reach 350MBps.”
Regarding QoS, Anderer says, “With trunked lines, multi-pathing iSCSI initiators, and logically isolated iSCSI traffic [using a VLAN and IPSec encryption], users can achieve highly secure and reliable IP SANs with Fibre Channel quality.”
Tony Asaro, a senior analyst at the Enterprise Strategy Group (ESG) research and consulting firm, says about 70% of all iSCSI-attached servers are using Windows, 9% use NetWare, 8% Solaris, and 6% Linux. Other versions of Unix primarily account for the remaining 7% of iSCSI environments.
“Microsoft’s dominance is a result of its aggressiveness when the iSCSI specification was solidified,” says David Dale, chair of the Storage Networking Industry Association’s IP Storage Forum (IPSF) and director of industry standards at Network Appliance.
“Microsoft developed a [free] software initiator to enable iSCSI on its operating system,” says Dale, “and they created a test in which hardware vendors qualify their hardware against Microsoft’s software. Very early on, Microsoft supported Multi-Path I/O (MPIO), which is a must-have for mission-critical SAN environments, host clustering, and ‘boot-from-SAN.’ ”
Microsoft’s decision to make an iSCSI initiator part of its standard server operating systems added legitimacy to the technology and helped to facilitate support from other vendors, according to Dave DuPont, senior vice president of marketing and business development at Sanrad, which sells switches and gateways for iSCSI environments. “If Microsoft supports iSCSI by providing initiators, it puts pressure on the other operating systems vendors to do the same.”
“Windows remains the largest segment of our customers’ operating-system platforms,” says John Joseph, VP of marketing at EqualLogic, an early player in the iSCSI market. “But our customers find out that with the software initiators provided on other operating systems, more servers can connect to the iSCSI storage devices.”
iStor, an iSCSI chip, board, and subsystems vendor, uses an IP SAN to run its entire business. Its server environment consists of Windows Server 2003 and Exchange for office productivity, Solaris file servers for engineering, Linux Red Hat Enterprise for Web services, SQL Server databases, and Unix and Windows file servers.
iSCSI is also supported on the increasingly popular VMware, which allows a single physical machine to run multiple virtual machines. VMware natively supports iSCSI, so coupled with an IP SAN, consolidation of both servers and storage results in better hardware utilization and performance.
According to ESG’s Asaro, there’s a misconception about where iSCSI is being deployed. He says most people believe iSCSI is being deployed in companies with 100 to 999 employees (which are typically considered SMBs).
However, “the largest segment that is installing iSCSI consists of companies that have 1,000 to 5,000 employees,” says Asaro. “The next group is probably where most people perceive iSCSI is installed-the 100 to 999 employee group. The third-largest iSCSI adopters are large enterprises with 20,000 or more employees.”
The number of deployments in the large enterprise category is growing, largely because of government regulations, such as Sarbanes-Oxley and HIPAA, which require organizations to retain and be able to access documents for a long period of time.
Jeff Whitney, VP of marketing at Intransa, another early player in the iSCSI market, says, “Fibre Channel is too expensive for enterprises to build out for compliance, and IT budgets are not increasing. These companies are adopting IP SANs.”
SNIA’s Dale says IP SANs in large enterprises are mainly found at the department level-often where the purchasing decision is made locally. He also sees IP SANs in large distributed enterprises that do not have mainframe environments.
“Large retail organizations with, say, AS/400s typically have dumb terminals and move tapes around,” says Dale. “We’ve seen pilots of iSCSI as the remote data-center solution for large retail organizations. They put an IP SAN in each store, and each SAN asynchronously mirrors to the core data center.”
In addition to large retail organizations, education and high-performance computing (HPC), which tend to be early adopters, are trying out IP SANs. Finance, telecommunications, and transportation are getting their feet wet as well. And IP SANs are making headway in video surveillance applications, medical imaging, and call centers with VoIP.
What’s motivating users to adopt iSCSI? ESG’s Asaro says, “Our research found that reducing capital and operational costs are the main motivators. Ease of management is right behind, which includes easier and faster deployment, leveraging existing IP skills, and overall, just easier management.” (For more on the management benefits of iSCSI, see InfoStor, January 2007, p. 40.)
Sanrad’s DuPont says that iSCSI is a cost-effective way to build storage networks that offer better data access and data protection than direct-attached storage (DAS). iSCSI is affordable because it uses Ethernet for block-level data transport, and IT staffs are familiar with Ethernet and IP so they can leverage existing skills to manage their IP SANs. And new volumes can be added dynamically as needed.
“CapEx and OpEx used to be pretty much the same amount,” according to Jay Kramer, VP of worldwide marketing for iStor. “Now OpEx is becoming 75% to 80% of the total budget. IP SANs reduce total cost of ownership [TCO] because they increase the productivity of IT departments and enable higher utilization of storage resources through virtualization.”
As data grows, sometimes at a rate of more than 100% per year, the problem of underutilized or overtaxed storage resources can be solved with a SAN as all of the storage capacity becomes available through the SAN. Extra capacity is not stranded in DAS systems.
ESG’s research shows that the majority of iSCSI users are storing file data (74%), database data (64%), and e-mail (50%).
Video surveillance is spurring growth in IP SANs where as many as 40 cameras write to storage at the same time and the data collected requires terabytes of capacity. IZON, an Adaptec iSCSI systems’ customer, designs digital security surveillance systems for airports, banks, schools, hospitals, factories, stores, casinos, and government facilities. IZON builds block-based iSCSI storage systems using industry-standard hardware along with the type of drives and RAID level that is appropriate for each customer.
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Faced with data growth from 3,600 users, Tony Wyland, director of network services at Messiah College, was constantly faced with the cumbersome process of adding Fibre Channel storage. In addition, the 1TB EMC Clariion disk array he was using was coming up for renewal. The cost to replace it was more than Messiah College wanted to pay. Now Wyland has three EqualLogic PS series iSCSI arrays-two in the main data center (8TB) and one across campus (4TB) for replication, mirroring, and disaster recovery. During installation, Wyland connected all of the servers- including Windows, HP-UX, Linux, VMware, and NetWare-to the new EqualLogic system, but also left them connected to the Clariion array until he was sure the new system worked the way he wanted it to. Now when users need more capacity, Wyland simply assigns a new IP address to the volume.
Landrum Human Resource Companies, a Sanrad customer, was anticipating data growth of 70% to 80% per year, and Jason Heuer, Landrum’s IT manager, knew that the company’s NAS system didn’t have the flexibility to keep up. At first he was wary of iSCSI, because he thought it would lead to latency and performance issues, but that has not been the case.
Currently, Landrum’s iSCSI SAN consists of two Sanrad V-Switch 2000 iSCSI gateways in a cluster connected to a 1.5TB Nexsan disk array. Heuer has four servers that access the SAN using Alacritech’s Gigabit TCP/IP offload engine (TOE) adapters, which provide iSCSI-TCP/IP acceleration.
“We access and store data on the SAN for several applications, including SQL, Exchange, electronic document management systems, and company documents,” says Heuer. “We have future plans to use iSCSI technology to replicate our data to other locations. Another benefit is flexibility: I can dynamically allocate storage to where I need it-when I need it-without disruptions to our production environment.”
LeftHand Networks’ Karl Chen, VP of channels and business development, sees many companies embracing iSCSI for somewhat novel applications. “Customers are using video streaming with a NAS gateway as an application server with a number of file and print applications being stored on IP SANs on the back-end,” says Chen. “They also use iSCSI for virtual tape library [VTL] disk backup and bulk storage around compliance in both legal and healthcare environments.”
Many companies that start out using IP SANs for Tier-2 applications, such as backup, then become more comfortable with the technology and start to trust it for Tier-1, mission-critical applications. For many organizations, e-mail is mission-critical and they expand their use of IP Storage to Microsoft Exchange environments. ESG’s research shows that approximately half of iSCSI adopters are using it for Tier-1, mission-critical applications.
Depending on whom you talk to, anywhere from 60% to 90% of servers are not connected to Fibre Channel SANs, and this means plenty of market opportunity for both Fibre Channel and IP SANs.
Recent figures from IDC point to widespread market acceptance and phenomenal growth for iSCSI SANs through 2010.
For example, IDC program manager Brad Nisbet expects a CAGR revenue for iSCSI from 2005 through 2010 of 74.8%, compared to 4.1% for Fibre Channel (although, of course, iSCSI started from a base of near zero in 2005). As for terabytes of data stored, IDC projects a CAGR of 159.2% for iSCSI, in contrast to 46.7% for Fibre Channel (see figure).
IP SANs offer many of the features that users of Fibre Channel SANs rely on, such as multi-pathing for performance and reliability, application-consistent snapshots to offload backup operations from the primary server, synchronous or asynchronous mirroring for fail-over, and remote copies for disaster recovery.
Currently, users have access to 1Gbps Ethernet products (although 10Gbps iSCSI products have recently entered the market) and 4Gbps Fibre Channel products, which may indicate that iSCSI is much slower than Fibre Channel. However, EqualLogic’s Joseph says the scaling of 1Gbps links between storage and servers continues to grow as more units of storage are added.
“The bottleneck between storage and servers is thought to be the network,” says Joseph, “but in typical [Windows] applications, the data transferred typically ranges between 20MBps and 60MBps. The 1Gbps link in an iSCSI connection is capable of 100MBps, so there’s plenty of bandwidth for multiple applications running simultaneously on a single storage system.
“We have customers running 20 to 30 different applications on a single storage system simultaneously and not saturating the wire,” adds Joseph. “The bottleneck is not on the network; it’s on the disk drives on the back-end of the storage system. They can’t produce enough data rate to fill the network connection.”
Many people associate iSCSI with low-cost, low-performance Serial ATA (SATA) drives, but Adaptec’s On-Target software, for example, supports Serial Attached SCSI (SAS) drives as well. And vendors such as EqualLogic, Intransa, and others offer iSCSI-based systems that support both SATA and SAS drives.
“The performance and reliability of IP SANs are being recognized in the user community,” says Mike DiMeglio, director of business development for Adaptec. “They’re comfortable that critical applications can now have the performance that’s required and the same functionality that Fibre Channel has offered in the past-especially when you add SAS disk support, which improves I/O performance and reliability, allowing users to incorporate IP SANs where they haven’t before.”
Concerning security, many experts think an IP SAN is as secure as, if not more secure than, a Fibre Channel SAN.
“IP SANs have data encryption, access, and control logs that allow servers to only connect directly with the LUNs they’ve been assigned,” says EqualLogic’s Joseph. “And 99% of our customers create a subnet for the SAN so it doesn’t burden the LAN with its traffic. This physical isolation of the sub-network is another barrier to a breach of security.”
Another way to ensure security is to create a virtual LAN (VLAN), an independent virtual network inside a physical network. The VLAN cannot exchange data with other data in the same physical environment without routing.
ESG’s Asaro says, depending on how the SANs are architected, there should be no difference in security between a Fibre Channel SAN and an IP SAN. “In some cases, security should even be better with iSCSI since IP networks have far more security features and capabilities.”
There seems to be no doubt that iSCSI and IP SANs are here to stay. In fact, some analysts think IP SANs will even win out over Fibre Channel in the long run, and others believe they will co-exist. It seems as if the only issue iSCSI has to work out is improving the performance and reliability of the attached disk storage in order to be a contender for the high-transaction, mission-critical applications found in larger enterprises.
“TCP has won against every protocol it’s gone up against, such as ATM and ARCNET, and it will probably be the same with Fibre Channel,” says John Matze, CEO at Siafu Software, which sells iSCSI appliances and software. “That’s because 10Gbps Ethernet is coming out, and the number of companies developing 10Gbps Ethernet is much higher than those developing 4Gbps and 8Gbps Fibre Channel.”
ESG’s Asaro says that today most iSCSI adopters and planned adopters will use iSCSI for new applications. “How- ever, this will change over the next three years,” he says. “Adopters intend to replace Fibre Channel with iSCSI to a significant degree [25% in a recent ESG survey] and to some degree [33%]. Over time we believe iSCSI has the potential to become the dominant interconnect. However, Fibre Channel will be around for a long time to come: There’s just too much investment from an infrastructure and human capital perspective.”
The IP Storage Forum (IPSF) is a marketing organization within the Storage Networking Industry Association (SNIA) focused on promoting adoption of IP-based SANs. The IPSF () includes vendors and resellers dedicated to providing the IT community with education on IP-based SAN solutions.
The SNIA IPSF maintains an IP Storage Solutions Directory ( age/soldir/) that highlights 10 areas where IP Storage is being deployed today and/or will be over the next few years, including the following:
Upcoming SNIA IP Storage events include:
April 16-19, 2007, San Diego
These one-day events offer an educational opportunity for both end users and channel professionals such as system integrators and VARs. Locations and dates include
April/May: Vancouver, Calgary, Montreal, Ottawa, Toronto June: Chicago, Minneapolis, Washington DC, Philadelphia
For more details, visit
InfoStor March, 2007