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Plugging into utility storage for enterprise-class application servers.

Today, whether we're at work or home, we don't think twice about plugging our appliances into electrical outlets to instantly receive the power we need. Everything from making coffee to powering factory equipment to building automobiles uses the same basic electricity. Electricity, water and phones are utilities, they are consistent wherever we go, are delivered with varying degrees of reliability, and we can have access to a lot or a little depending on out needs. The concept of "utility" services has not escaped IT professionals within large organizations. After all, every house in America does not have its own power plant so why should every department within a large organization have its own IT infrastructure?

Removing data from workflow and departmental servers and delivering storage to those servers like a utility has been an IT goal for the last 10 years. Server captive data is difficult to protect, reallocate, share and reproduce when it's kept on disk drives within individual servers.

By delivering data storage capacity as a centralized utility you not only remove the data from the server and centralize it onto a network, but you can eliminate or greatly reduce the number of disk drives directly attached to workflow servers. Utility storage delivers:


* A fast and highly reliable infrastructure where data resides away from the server

* Centralized data protection and security

* Infinite storage capacity that can be resized, reused, reallocated and shared

* Agent- and license-free storage services to deliver different grades and levels of capacity for hundreds of individual and distributed servers.

There are many IT professionals considering an iSCSI IP SAN as a means to finally deliver their utility storage services to large numbers of application servers. The latest quarterly storage numbers from International Data Corp. show tremendous momentum in iSCSI. The market showed a 32 percent revenue growth over last quarter. In 2003, worldwide iSCSI revenue amounted to $18 million. In 2004 this soared to $113 million.

Surprisingly, many small businesses are not interested in utility storage. They have a low number of servers and small IT departments. They don't need to build a storage utility model to service multiple departments and large numbers of servers. Small businesses are interested in simplicity and low costs, and will generally select an entry-level iSCSI array. iSCSI arrays, like NAS systems, are single systems that can centralize storage for a small number of attached servers. But a single iSCSI array represents a single point of failure, can be difficult to scale and limits performance to that of the individual system. In contrast, large businesses deploying utility storage are more concerned with performance, efficient storage utilization, guaranteed storage availability and future scalability costs. Storage area networks or SANs, based on IP, represent the more popular way of interconnecting a large number of application servers with different classes and grades of storage systems.

Because SANs are networks, they are open and support all popular server operating systems, applications and storage systems. Before any user decides on the appropriate utility storage solution, they should consider the architectural attributes of an IP SAN. There are three basic attributes that distinguish IP SANs from iSCSI storage arrays. These IP SAN attributes are continuous real-time data access even during component or system failure, low scalability costs to maintain a consistent CAPEX over time and the ability to deliver high peak load performance to a large number of utility storage customers. Because IP SANs deliver these three key attributes in addition to the utility properties of iSCSI, they are becoming a popular network-storage solution for IT professionals seeking utility storage. (Figure 1)


Utility storage, like electricity, needs to deliver the required data performance to the application server. After all, slow electricity would halt your appliances and slow data performance would halt your application servers. IP SANs are designed to sustain high levels of random read and write operations. Intelligent IP SAN switches have high-speed architectures utilizing network processors, real-time operating systems and powerful backplanes. A single IP SAN switch can sustain 300MB/sec or 600MB/sec (when clustered) of random read and write requests and well over 60,000 IOPs. This delivers raw random read/write performance that is from 4 to 15 times greater than small arrays and can easily support from 10 to 200 standard application servers. IP SANs can utilize any type of storage system. This allows the IT professional to select the storage systems that best fits the performance and reliability needs of varying application servers receiving utility storage. For example, you can use a storage system with FC drives rated for 200 MB/sec and 10,000 IOPs for application servers requiring high performance, and use a SCSI storage system with ATA drives rated for 40MB/sec and 3000 IOPs for application servers requiring lower performance.

In addition to selecting different classes of storage (different cache and drive types), IP SANs can simultaneously read and write data to multiple independent storage systems. By spreading server volumes across independent storage systems and being able to directly access those storage systems without having to pass through another control layer, IP SANs can maintain line speed performance to the storage systems (up to 2GB/sec, 200MB/sec, 20,000 IOPs per storage system) regardless of the location of the data. Moreover, since the storage systems are independent of the intelligent IP SAN storage switches, capacity and performance can be increased by simply adding more storage systems.

IP SANs deliver consistent CAPEX over time because they are not limited to any specific type or brand of storage array, enabling IT professionals to select the type of storage systems that best fits different business applications--any interface, cache, drive type or component redundancy. IP SAN performance is not affected when more arrays are added to increase capacity. In fact, IP SAN performance can increase with more arrays because random read/write requests can be simultaneously spread and processed by multiple storage systems.

Guaranteed Data Availability

IT professionals realize that moving data from dozens to thousands of individual application servers to a utility storage model would create significant business problems if the utility storage service were to become unavailable because of a component failure. Lost access to data, like lost access to electricity would bring most businesses to a complete halt.

IP SANs use clustering technology to create system fail-over and fail-back scenarios among IP SAN storage switches. In addition to system redundancy, real-time (synchronous) data mirroring to independent storage systems provides a highly persistent and fault tolerant data environment. Host-site creation is very simple when combining real-time data mirroring and clustering found in IP SAN storage switches. IP SAN storage switches can also replicate data across long distances using iSCSI over IP networks (LAN, MAN, WAN). Using PIT (point in time) technology, groups of write commands are compiled into PIT files, which are transmitted to other IP SAN storage switches. PIT technology provides time/data consistent application mount points for application servers.

Cost effective Scalability

IP SANs, by their nature, use an open architecture and are much more cost effective to manage and scale. IP SANs do not limit the number of application servers that can connect to the architecture. IP SANs that use IP SAN storage switches do not require agents or license fees for each added server. So the IT professional does not have to pay fees in the future as they add more and more application servers--year after year to the IP SAN. Large scale IP SANs can scale to 250 servers without requiring any additional IP SAN infrastructure expenditures. Adding storage capacity is similar to adding servers. The IP SAN storage switch has no practical limit to the number of custom volumes it can create and capacity it can manage. Leading IP SAN storage switches allow IT professionals to scale their capacity to more than 4000TB (4 petabytes) and can create and manage over 50000 unique volumes. Since the IP SAN storage switch is in the network layer, there is no cost associated with the IP SAN storage switch when adding more disk drives, disk enclosures or arrays to increase the available capacity pool. Because the IP SAN storage switch is agnostic to the storage brand and has FC, SCSI and IP ports it can support most storage interface protocols and drive types (FC, SCSI, SATA, ATA, iSCSI) the user has the freedom to select any disk storage supplier he wants for increasing the storage capacity and can take full advantage of the continuing reductions in drive capacity prices allowing you to maintain a consistent CAPEX.


The concept of "utility" storage services is now a realistic and affordable option for more businesses than ever because of the cost advantages that IP SANs bring to enterprise storage networking. Using iSCSI and an IP SAN architecture, storage becomes a utility; simply plug your servers into the network and you will receive consistent and reliable storage capacity for any application Like a utility, storage is consistent and compatible with all applications; it can be delivered with varying degrees of reliability and can be increased and recycled to meet diverse business needs.

Zophar Sante is vice president of market development at SANRAD Inc., San Francisco, CA
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Title Annotation:Storage Management
Author:Sante, Zophar
Publication:Computer Technology Review
Geographic Code:1USA
Date:Aug 1, 2005
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