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VMware to add memory compression, I/O resource management to next vSphere

The upcoming VMware vSphere release promises improved I/O resource management and memory compression, according to attendees of VMware's Partner Exchange.

The next release of VMware's vSphere will add memory compression, I/O resource management and better VMotion performance, according to attendees of last week's VMware Partner Exchange in Las Vegas. If the company architects these features as promised, they could improve performance and resource utilization of VMware environments.

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In the next version of vSphere,VMotion will increase the number of concurrent live migrations from a default of two in vCenter 4.0, up to as many as eight. With modification, it's possible to achieve up to six simultaneous VMotions per host with vSphere today.

IO-RM (IO-Resource Manager), meanwhile, will extend VMware Distributed Resource Scheduler (DRS) to look not only at CPU and memory utilization but also at I/O traffic per VM and set limits on the amount of I/O a virtual machine (VM) can use, or it can prioritize its consumption relative to others in a data store, attendees said.

The problem of multiple VMs contending for I/O is real, said Rich Brambley, a vExpert and the author of the VM/ETC blog. The issue "generally surfaces when two or more VMs that generate significant I/O per second, or IOPS, mistakenly get placed together in a LUN [logical unit number]." With a good up-front design, "you really shouldn't need it, but if you do unexpectedly find yourself in that situation, this tool will help you referee that resource contention."

The problem of multiple VMs contending for I/O is real.
Rich Brambley,
vExpert and  VM/ETC blog author

But unlike the existing DRS, IO-RM does not yet dynamically move an I/O-constricted VM to a different host or data store using VMotion or Storage VMotion, Brambley added. "That's the next step, and when they get there, it will be really cool. But from my understanding it's not available yet."

Finally, with Transparent Memory Compression, the hypervisor will compress memory on the fly to increase the amount of memory that appears to be available to a given VM.

The new Transparent Memory Compression feature will be of interest in the case of workloads where memory -- rather than CPU cycles --has limitations, said Gordon Haff, the principal analyst at Illuminata Inc. in Nashua, N.H. That's the case more often than not in virtual environments.

"We have lots of CPU horsepower, but not necessarily as much of the other things," Haff said. Assuming that the overhead associated with memory compression is reasonable, "you can very easily see giving up some processing power."

Without knowing what the overhead associated with memory compression is, however, it's hard to say how relevant the memory compression feature will be.

"We've had the algorithms to do compression/decompression for years," Haff said. "The problem is the performance associated with it." Haff noted that IBM includes memory compression -- the so-called Active Memory Expansion feature -- as part of its new Power7 chip. But unlike VMware's Transparent Memory Compression, which will presumably be a software-only solution, the Power7 version runs in hardware to minimize CPU overhead.

On tap for 'vSphere'?
Exactly when these features will be released remains unclear.

One VMware partner at the show said that the demo of IO-RM in VMware CTO Steve Herrod's keynote showed that it was well beyond the lab.

"It looked complete. It was integrated in to the [vSphere] Client," he said, and could very well be included in the next version of vSphere that is rumored to be available in time for VMworld 2010 next fall. Already, a few select partners have been invited to participate in a very early private beta, he said.

What that release will be called is also unclear, said a beta participant. "Four-dot-one, 4.5, -- whatever they decide to call it."

Let us know what you think about the story; email Alex Barrett, News Director at, or follow @aebarrett on twitter.

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