InformationWeek
Defining The Business Value Of Technology
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October 2, 2000 |
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Storage Area Networks
Everything In Its Own Place
Storage area networks are effective storage solutions, but making them work seamlessly requires planning and hard work. Interoperability suffers for throughput, and managing them isn't for the weak of heart. System integrators can expect to do well for years.
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-business applications require a trio of factors in great abundance: high performance, high availability, and scalability. Business partners, suppliers, and customers often demand near-continuous access to business data.This means that data-storage systems must be designed to maximize data storage and access tasks. An increasingly popular storage optimization strategy is the use of a storage area network, which makes every storage device on a network accessible to all of a network's servers.
Storage area networks are relatively simple in concept, although they're not quite so simple to implement. A SAN is a subnetwork made up of heterogeneous storage resources and servers tied together with a high-speed connection. While a SAN is often an effective storage solution, sharing data between servers, managing storage across heterogeneous server platforms, and getting Fibre Channel devices from different vendors to work together is seldom an easy proposition.
A SAN consists of one or more storage devices, a switch or hub, adapters in the servers, plus backup and management. What makes a SAN difficult to manage? All of its components are designed for maximum throughput, often at the expense of interoperability.
To learn the state of the art, InformationWeek recently conducted tests of four SAN products at the University of Hawaii's Advanced Network Computing Lab. Our tests show that managing the finished SAN can be difficult. All the tested products work, but they offer very different levels of integration and functionality.
We tested products integrated by QLogic Corp. and Interphase Corp., and two products from Compaq. Prices as tested range from $19,543 to $143,787 for 150 Gbytes to 764 Gbytes of storage. These numbers represent a range of capabilities, from a basic SAN that would be appropriate for a small graphics department to a system that can handle the demands of a large global company.
The more-expensive Compaq products include much greater capacity, a tape library, and a storage router. The Interphase product includes a single tape drive and storage router, while the QLogic product lacks a tape drive and management software.
The Compaq products include support for Sun Microsystems' Sparc server, which the others don't have. They have capacities comparable to the others but without the Sun compatibility and Compaq's tape library are inexpensive. Compaq products also include the best management package.
Other items that make a big difference in cost are the hub or switch and the type of storage. Fibre Channel switches are two to three times more expensive than hubs for the same number of ports. They provide the same advantages as Ethernet switches--problems are limited to a single port on the switch, rather than every device connecting to the hub. In addition, overall performance is higher because each port has 1 Gbps of throughput, rather than the whole hub sharing one gigabit per second of throughput.
Some of the storage devices are redundant arrays of independent disks, while others are "just a bunch of disks, or JBODs." A RAID device has inherent redundancy: A disk in the array can fail without loss of data. The alternative doesn't have this capability, although it can be added through software on the server or storage controller. RAID is more expensive than a JBOD because it has an integrated controller.
We asked the vendors to bring two storage devices with at least 150-Gbyte capacity, one tape drive, at least one SAN switch, a management application, one server, and host bus adapters for two more servers, including a Sun workstation and Linux server. The test scenario was designed to simulate a typical heterogeneous SAN environment, with either Windows NT or Windows 2000 servers and either Sun Solaris or Linux servers.
The test's primary focus was to evaluate the SAN as a complete product--not to test throughput per se, but to look at manageability, interoperability, and ease of setup and use. We found that SANs are a viable technology today but aren't for the faint-hearted. A heterogeneous product with multiple vendors supporting multiple platforms and one that encompasses management and ease of use isn't yet available. This is an area in which systems integrators will continue to make good margins for the next few years.
Compaq's MA8000 is the best, most complete SAN product we looked at. Compaq not only provides all of the pieces asked, but it's the only company to demonstrate compatibility with non-x86 servers and to offer a complete and integrated management product. On the other hand, the Compaq products are Compaq-only, in spite of the vendor's "Open SAN" claims. Using its host bus adapters in non-Compaq servers isn't supported, although it should be possible. Everything is Compaq-branded, other than the Sun workstation used to test non-x86 compatibility, and Compaq resisted suggestions that we test with other vendor's equipment.
The smaller of Compaq's products, the StorageWorks RA4100 SAN, is geared for a handful of servers. It's cost-effective, with good management tools, but has limited expandability. Connectivity within the RA4100 is through the Compaq Fibre Channel Arbitrated Loop Switch 8, which normally contains eight ports but can be upgraded through an expansion module with three additional ports. The switch that Compaq brought to the test has all 11 ports.
The RA4100 is designed only for x86-based servers. Compaq brought a ProLiant 8500 equipped as a four-way Pentium III Xeon machine running Windows 2000 Server. We also used two Compaq servers: a ProLiant DL380 running Red Hat Linux 6.2 and a DL580 running Windows 2000 Server.
Compaq declined the Dell PowerEdge 4400 and HP NetServer LH6000 we offered to demonstrate multivendor interoperability. Each of the servers was configured with a Compaq Fibre Channel host bus adapter, which requires a 66-MHz 64-bit PCI slot. According to Compaq, its SAN supports Banyan, NetWare, OS/2, and Windows NT 4.
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