SANs drop the shackles

Today's enterprise SANs are measured in multiple terabytes as IT executives push size, complexity and functionality to the limit. The sprawling nature of these networked environments is driving the adoption of new and emerging technologies. One of them is an IP-based storage solution which complements Fibre Channel. Sandra Rossi reports

IP storage made huge advances in 2005 with iSCSI reaching mainstream acceptance. Analyst firm IDC estimates more than 6000 customers worldwide have deployed iSCSI-based SAN solutions. And the market is expected to experience 211 percent compound annual growth for the next three years, topping $US2.65 billion in 2009. David Dale, chairman of the Storage Networking Industry Association's (SNIA) IP Forum in Australia, said most iSCSI deployments today are on Intel-architecture servers running Windows.

However, NetWare and Linux environments are also becoming popular for iSCSI, and solutions for small RISC servers running Unix are just starting to emerge.

"The driving force behind a transition from DAS (direct-attached storage) to an IP SAN is often high data growth and the need for operations efficiency. In these circumstances the legacy DAS environment becomes increasingly complex; backup/restore operations become increasingly unreliable, and the storage environment is unable to support the demands of the business," Dale said.

Since iSCSI is a SAN protocol, it was initially seen as an adjunct to Fibre Channel SANs.

"It was usually characterized as a less-capable technology that would connect stranded servers into the corporate SAN. On the other side of this argument were iSCSI proponents who viewed it as a disruptive technology that would render Fibre Channel obsolete as a SAN interconnect. The reality lies somewhere between these extreme perspectives," Dale said.

To date, iSCSI and FCP (the Fibre Channel SAN protocol) have often turned out to be complementary technologies - each having a distinct place in the IT infrastructure as a SAN alternative to DAS. Fibre Channel generally provides high performance and high availability for mission-critical applications, usually in the corporate data centre. In contrast, iSCSI has generally been used to provide SANs for business applications in smaller regional or departmental data centres.

Because NAS and iSCSI transmit storage traffic over Ethernet, there was initially some confusion about the technologies.

From an application perspective, Dale said iSCSI-based SAN storage looks just like DAS and so it works transparently with all applications.

"NAS will usually work fine, but since it is a different paradigm it generally needs to be supported by the operating system vendor and qualified by the application vendor," he said.

Since snapshot functionality is so common with iSCSI, most deployments back up from a recent point-in-time copy, which eliminates the traditional backup window.

But second-generation iSCSI solutions will expand on these capabilities.

Dale said second-generation iSCSI hardware initiators add support for active-active multi-pathing configurations, boot-from-SAN capability, and improved CPU offload. In addition, second-generation iSCSI software initiators improve the support of high-availability environments with multi-pathing, fail-over, and host cluster services support.

The biggest storage array in the world, which is currently under construction, will have capacity equivalent to a stack of iPods three times the height of the Empire State Building. Interestingly, it will be managed with common Ethernet networking tools.

The SAN will support a project called the Human Speechome Project - for the MIT Media Lab -which is expected to archive and search 1.4 petabytes of data over three years.

The SAN is being built from commodity hardware and uses a 10GbE IP network for data transfer between the backend SAN and hundreds of servers.

Computing infrastructure is expected to be composed of more than 300 Hammer Z-Rack storage enclosures from Bell Microproducts, about 3000 SATA (Serial Advanced Technology Attachment) hard disk drives from Seagate Technology and more than 100 10GbE switches and 400 blade processors from Marvell Technology Group.

The high-throughput switches are needed for the storage I/O anticipated by researchers who believe they'll be processing 700TB of data during every 12-hour analytical run. To achieve the desired performance requirements, 150-drive stripes (aggregated virtual volumes) will be created using the native virtualization capabilities of Bell's Z-SAN. Protection against data loss will be delivered through RAID 10 mirrors (duplicate copies) of the raw video data, transform data, and metadata files. - with Lucas Mearian

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More about Bell MicroproductsBillionDASIDC AustraliaIntelMarvell Technology GroupMITMIT Media LabParadigmSeagateSeagate TechnologyStorage Networking Industry Association

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