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Blades and the back end
Arun Taneja, founder and consulting analyst at the Taneja Group in Hopkinton, MA, says the IT industry is just catching on to the power of blades and virtualization. According to Taneja, there's recognition within IT that today's blades are powerful enough to run VMware. "When I just had single-processor, low-performance blade servers, the concept of virtualization and server blades" weren't directly connected, he says. "Now we have powerful enough server blades that if you get 10 or 12 blades, you can create a good number of virtual machines."

But with systems that share network modules (the equivalent of a network card on blades) against multiple blades (i.e., 10 blades across four network modules), many IT pros will ask "Who gets the access?" says Stephen Foskett, director of data practice at Mountain View, CA-based consultancy Contoural Inc. "People are very interested in the impact of VMware on storage because it makes use of a lot of back-end I/O," he says. "You can get a four-port NIC card and, in some cases, you can even get each blade a new port. That leads users to start looking at 8Gb Fibre Channel [FC] and solutions like virtualized InfiniBand. Those two things--8Gb or 10Gb Ethernet cards, and InfiniBand--come from this idea that we're pushing all this through the same pipe in the back end."

With multiple virtualized servers

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sharing the same FC attachments, Contoural's Foskett is predicting a surge in popularity in N_Port ID Virtualization (NPIV) technology, which essentially lets users virtualize their host bus adapters (HBAs). "If you have more than one instance of an operating system running on the other side of the port--as you do with virtualization--suddenly it might not be a good idea to have one, two or 20 servers using the same N_Port ID. There are ways you can keep them from seeing each other's storage," he says. "But, basically, it's a bottleneck problem."

With NPIV, a virtual N_Port ID is assigned to each server. This is important because users can move a port and that port name will follow. Indeed, Foskett is predicting a "perfect storm" collision of 8Gb FC or 10Gb FC over Ethernet (FCoE), N_Port ID and virtualized servers as more users adopt blade strategies and combine them with virtualization. This technology storm is gathering strength around blades, rather than standalone servers, because of the way blades share resources, he says.

"Blades share physical resources on the back end," says Foskett. "With blades and server virtualization, you can have more than one server or more than one instance of the operating system all passing through a single interface. Therefore, they can oversubscribe those resources and make demands on them that can't be met."

Even though NSCU's Chau is ready to run a new banking system on his blades, he cautions anyone investigating blade strategies that it "definitely brings more complexity to the environment." NSCU is revamping the hardware architecture to support its BI initiative by implementing four HP ProLiant BL680c G5 Server blades. One runs Microsoft SQL Server 2005, and there is one each for SQL Server 2005 Analysis Services, Reporting Services and Integration Services. (Those blades are quad-core x 4 sockets, and 64GB RAM, with all connecting back into a HP Storage- Works EVA 8100 array.)

"There has to be some sort of application profiling," says Chau. "For example, SQL is I/O-intense and file printers are not that intense. So you have to mix and match. You can't just rely on the hardware infrastructure and what it can do. You have to do some performance profiling or there comes a point of diminishing return," he adds. (See "Performance tips," below.)

Performance tips
North Shore Credit Union (NSCU) in North Vancouver, British Columbia, is currently revamping its hardware architecture to support its business intelligence (BI) initiative by implementing four Hewlett-Packard (HP) Co. ProLiant BL680c G5 Server blades. One runs Microsoft SQL Server 2005, and the company has designated one each for SQL Server 2005 Analysis Services, Reporting Services and Integration Services. Each of NSCU's HP Blades is configured with multiple host bus adapters (HBAs) to leverage the multipath efficiencies.

Here are NSCU's tips for optimizing performance.
  • Bring on the disks. It's better to have many disks with lower capacity than it is to have fewer disks with higher capacity.

  • Create multiple disk groups to better align with your application needs. For example, to support its complex BI strategy leveraging SQL Server 2005, NSCU incorporates three disk groups: one each for data, logs and tempdb.

  • Zoning. Allow for dedicated disks in the SAN for isolation of I/O on the LUN allocated for SQL.

  • Sector-align disks for optimum I/O. NSCU uses the 64KB alignment parameter.

This was first published in July 2008

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