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IBM's Nehalem EX-based systems to boost x86 server memory capacity

The new"ex5" server architecture, which is based on IBM's upcoming eight-core Nehalem EX x86 processor, increases memory capacity to boost server virtualization ratios.

IBM's new "ex5" architecture for Nehalem EX-based x86 systems will boost server memory capacity to accommodate virtualized data centers, but at least one end user wonders whether it's too much of a good thing.

This week IBM said its System x servers based on Nehalem EX -- which are due out by the end of the month -- will include up to 32 additional dual-inline memory modules (DIMMs). With each DIMM capable of holding up to 16 GB of RAM, that's a total of 512 GB extra of RAM per server, which the company said would probably be twice as much as that offered by the competition.

Its importance, IBM said, is that applications in virtualized environments are often memory-starved, even as the processor provides plenty of power for all to share. IBM plans to roll out these servers over the course of the year.

Another benefit that IBM has touted is the potential to reduce VMware licensing costs, or keep them level, by providing the ability to fit more virtual machines on a chip. Since VMware charges by the socket, if end users can pack more VMs in, they might save on licensing costs. One caveat: End users running VMware vSphere on Nehalem EX may run into higher licensing costs because the chip has eight cores. VMware's multicore pricing and licensing policy states that costs can increase with servrers running on chips with more than six cores.

More server memory capacity; too much of a good thing?
Kenny Coleman, a VMware administrator at a Louisville area nonprofit, said the extra memory capacity seems nice on the surface, but putting more VMs onto fewer sockets could have drawbacks as well. That would mean having to manage a lot more VMs on a single host. meaning "consolidation ratios would be outrageous," he said.

"Does saving money on licensing make up for the fact that the environment could be less redundant?" Coleman asked. "I guess it depends on how much you like your job. If a host does fail, can you imagine restarting 250 VMs?"

Coleman oversees a relatively small shop that runs VMware ESX on two IBM x3652 rackmount servers. The servers run on Intel Xeon 5530 quad-core, 2.4 GHz Nehalem chips, with 48 GB of RAM and thus far host about 11 virtual machines.

Still, Ideas International Inc. analyst Tony Iams said memory in virtualized environments is valuable.

"If you talk to people who manage virtual machines, you'll find out that memory is one of the most precious resources in many cases," said Iams, who also wrote about the issue. "Most workloads are not CPU-bound. Now they won't be as memory-bound. They'll have the economic benefit of being able to add more virtual machines per server."

IBM currently ranks third in x86 server revenue share behind leaders Hewlett-Packard Co. and Dell Inc., according to the most recent figures from IDC. HP has about 39% share, while Dell and IBM have about 20% each. IBM has gained share, however, and over the past year has increased by 3.5%.

Iams added that no one knows whether IBM's ex5 architecture is truly unique until all the vendors unveil their Nehalem EX-based servers, and IBM has done "something a little differently" by essentially announcing its servers before the chip is officially announced. But in general, Iams said, IBM has tried to add to the industry-standard Intel chipsets on the x86 side.

Mark Fontecchio can be reached at

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