The State of iSCSI: Continued Rapid Market Growth and Expansion Beyond Windows Stronghold
By David Dale, Industry Evangelist & Director Industry Standards, NetApp; Chair SNIA IP Storage Forum

Introduction
Over the past year, we have seen continued rapid growth in the market for iSCSI storage around the world. The bulk of this growth has been in the Windows market, as iSCSI SAN solutions continue to displace Direct Attached Storage. However, we are now starting to see significant traction in other host environments and across a broader range of applications.

This article looks at the state of the market, typical deployment environments and best practices. It also describes new market growth segments, and gives some hints on what to look out for in the coming year. Finally, it describes SNIA's IP Storage activities and summarizes what's new with the SNIA IP Storage Forum.

First, however, a brief positioning with respect to other technologies.

Definitions and Positioning
The term "IP Storage" is generally used to refer to a Storage Area Networking (SAN) solution that uses standard ethernet connectivity in some way. These solutions fall into two categories: those that use an ethernet link to interconnect Fibre Channel SAN environments via gateways (the protocols involved here are FCIP and iFCP), and those where a SAN is built using Gigabit Ethernet infrastructure instead of Fibre Channel - using the iSCSI protocol. So, iSCSI is a SAN protocol - a standard disk storage protocol, just like SCSI and FCP (the primary protocols that host operating systems use to communicate to attached storage devices), sometimes called block storage protocols.

There seems to be some confusion over the difference between IP Storage and Network Attached Storage (NAS), since they both transmit storage traffic over Gigabit Ethernet infrastructure. NAS solutions differ in that they use file-access protocols such as Network File System (NFS) and Common Internet File System (CIFS), and were originally designed for file sharing applications, where servers or users access network-based shared files.  From an application perspective, SAN storage looks just like direct-attached storage to the host OS, and so it works transparently with all applications. NAS will usually work fine, but since it is a somewhat different paradigm, it generally needs to be qualified by the application vendor. However, since it is a much more highly virtualized storage environment, the ease-of-management benefits with NAS can be significant.

To date, iSCSI and FCP (FC SAN protocol) have turned out to be largely complementary technologies - each having its distinct place as a SAN alternative to direct-attached storage. Fibre Channel generally provides high-performance, highly available SAN solutions for mission critical applications in Tier 1 and Tier 2 data centers. iSCSI, on the other hand, is generally used to provide simpler SAN solutions for mission critical applications in small and medium enterprise (SME) environments and for enterprise applications in regional, departmental and Tier 3 data centers in large organizations.

This situation is changing, however, as iSCSI breaks out of its Windows stronghold and gains traction in heterogeneous host environments. An ever-growing number of deployments, and the emergence of large-scale and high-performance solutions on 10 Gigabit Ethernet (10 GbE) infrastructure, are also driving this change.

State of the Market
The iSCSI market has been tracked by IDC (IDC Storage Tracker) since 2004 - and has consistently been identified as the fastest growing segment of the storage market. IDC assessed the market size at about $530 million in 2006 - shipping 445 PB - and achieving a 70% year-over-year growth rate. A similar annual growth rate is expected over the next few years, as the remainder of the storage vendors offer native iSCSI storage solutions, and host environments beyond Windows become mainstream.

In terms of the number of IT deployments, Enterprise Strategy Group estimates that 2,500 IP SANs were deployed by the end of 2004, rising to 10,000 by the end of 2005, and more than 20,000 by the end of 2006.

The factors driving this growth have been the continuing need for IT organizations to do more with less - less capital cost, fewer admins per Terabyte, less complexity - coupled with continuing data growth, emerging best practices requiring strict and comprehensive data retention, and the recognition that even Tier 2 and 3 applications are mission critical in today's 7x24 world. Interestingly, these factors affect enterprises of every size, and most IT managers now recognize that yesterday's direct-attached storage architecture simply cannot meet the needs of today's business environment.

Typical Deployment Scenarios
Initial IP SAN deployments were most often at the departmental level of larger enterprises, particularly in Windows environments comprised of smaller servers where limited admin support, host attach costs and infrastructure complexity have traditionally inhibited Fibre Channel SAN deployment.

iSCSI-based IP SANs have also become extremely popular in large organizations with either distributed resources or widely distributed data. The combination of affordability, an existing high-speed ethernet infrastructure, and ethernet-savvy IT administrators, coupled with array-based data protection and data management capabilities such as snapshots, remote copy and asynchronous mirroring, enable these organizations to easily build out efficient multi-location integrated data management environments.

More recently, we have seen the adoption of IP Storage solutions in medium and even small organizations - once again replacing direct-attached storage and supporting Windows-based business applications. In many cases, these applications are mission critical, and the major customer concerns are data growth, data availability, the need to more efficiently manage the environment with existing admin resources and limited IT budgets.

Best Practices
Now that the industry has a significant number of real-world iSCSI deployments, a number of "best practices" are now becoming evident.

One early assumption was that iSCSI SAN solutions would simply be cheap SAN storage with limited functionality. This seemed like a reasonable assumption at the time, since entry-level Fibre Channel arrays lacked the sophisticated data management capabilities of their mid-range and high-end cousins. Interestingly, however, almost all first-generation iSCSI-native arrays provided sophisticated data protection and even disaster recovery capabilities, including snapshots, mirroring and distance replication. Two significant "best practices" resulted from this.

ELIMINATION OF THE BACKUP WINDOW
Since snapshot functionality is so common with iSCSI storage, most deployments back up from a recent point-in-time copy. This completely eliminates the traditional back-up window. Data recovery is also extremely fast when recovery can come from the disk-based point-in-time copy. The savings in admin overhead and end-user downtime from these features alone can justify the entire IP SAN investment. In addition, the wide availability of remote copy technology is resulting in the widespread use of disk-to-disk backup, with tape becoming an archive medium in a centralized facility. This makes it possible to automate the backup of remote data assets in satellite data centers and remote offices.

AFFORDABLE DISASTER RECOVERY
With the broad availability of distance mirroring technology with iSCSI storage systems, even small and medium-sized enterprises can affordably implement a practical disaster recovery plan. This usually involves taking snapshots at regular intervals during the day, and using remote copy or asynchronous mirroring to copy the changes to a remote system. Since everything is IP-native, there is no need for the cost and complexity of gateways and protocol conversions, and the solution can be designed to fit the required service level of the applications at that particular facility.

SECURITY
Two IP SAN topologies seem to have emerged, each with its own security best practices. In one topology, the IP SAN has its own Gigabit Ethernet switch, and the SAN is a private network, completely separate from the data communications network, in a secure data center. Standard iSCSI authentication takes care of access permissions between servers and Logical Unit Numbers (LUNs). In the second topology, the IP SAN uses existing Gigabit Ethernet infrastructure. In this case, a subnet is defined, storage access is to defined-function ports, and Virtual Private Networks (VPNs) are often used to separate and protect traffic between any particular application server and its accessible storage. Today, in the Windows environment, you can configure an IP SAN environment that is every bit as secure and resilient as its Fibre Channel SAN equivalent. In addition, the Unix vendors and the Linux community are catching up with native storage stack support for iSCSI, including multipathing and clustering, so equivalent resilience is becoming available this year for those environments.

New Market Segments
There are still very large amounts of direct-attached storage in Windows server environments of all sizes. IP SAN solutions are expected to continue to convert these to networked storage environments. In addition, new IP Storage capabilities will further expand the reach of IP Storage solutions. The following are among the more interesting of these new capabilities:

• VIRTUAL SERVER ENVIRONMENTS
  iSCSI-based SAN solutions are becoming very popular, here. In particular, VMWare ESX has robust support for iSCSI storage, and is seeing significant deployments.
• UNIX AND HETEROGENEOUS HOST ENVIRONMENTS
  As complete native iSCSI host support for UNIX and Linux has emerged over the past year, we are starting to see significant deployment in departmental UNIX and heterogeneous OS environments - particularly those built on blades and smaller servers.
• UBIQUITOUS BOOT-FROM-SAN
  The broad availability of both hardware and software iSCSI SAN boot is now driving the growth of IP SAN solutions in high-density and blade server environments. There is a great deal of interest in both large scale and small scale blade deployments.
• 10 GIGABIT ETHERNET
  The availability of 10 GbE connections on many mid-range and high-end iSCSI arrays, in combination with the availability of more affordable 10 GbE connectivity, is starting to drive IP SANs in high-performance and large-scale aggregated storage environments.

• Lower-cost 10GbE TCP/IP Offload Engine (TOE) solutions will become available in the coming months, with software offering offload options to NICs, CPUs, or specific cores on CPUs. This will drive IP SANs into more application areas.
• The "Data Center Ethernet" activity in the IEEE promises to improve both performance and latency for all Ethernet-based protocols.
• The "Fibre Channel over Ethernet" activity in T11 will increase interest in 10 GbE as a "unified" data center fabric. This is likely to have a positive "future-proofing" impact on both existing Fibre Channel environments and on "greenfield" iSCSI data center deployments.

SNIA and IP Storage
SNIA continues to be active with IP Storage activities, in both the IP Storage Technical Working Group and in the IP Storage Forum.

The Technical Work Group continues to be involved in driving iSCSI support into SMI-S, and is also engaged on the creation and standardization of the iSCSI Management API (IMA).

The IP Storage Forum maintains its focus on driving the broad adoption of IP-based SAN solutions through education, promotion,and events around the world. Over the past year, we have made significant improvements on our external Web site, with the addition of a Product Showcase and a Solutions Directory. We have also broadened vendor participation on the leadership team with the appointment of four new Committee Chairs - responsible for Education, End-User Liaison, Technical Liaison and Membership. If your company has an IP Storage product strategy, now is the time to join us and help grow the market.

About the Author
David Dale is director of Industry Standards at Network Appliance, where he drives standards participation, represents NetApp in industry organizations, and acts as a technology spokesperson. With over 20 years experience in the computer industry he is a member of the SNIA Board of Directors and Chair of the SNIA IP Storage Forum.