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VMware users pack 16 VMs on each server, despite memory limits

Jon Brodkin | Dec. 15, 2010
VMware customers run an average of 12.5 virtual machines on each physical server, but high levels of consolidation are driven in large part by proliferation of multi-core servers, and memory limitations may be preventing further progress.

VKernel also examined CPU and memory utilization in the virtualized data centers. Virtualization can effectively let IT allocate more memory and CPU to applications than physically exists in the data center, because resources can be shared across a pool with applications usually not using their entire allotment.

But while organizations are allocating more than twice as much physical CPU capacity as they actually own, they are only allocating about 70% of memory capacity. Businesses may have good reasons for under-allocating memory - for example, they might want a buffer in case of failover situations, Semple says.

But the 70% figure could also indicate inefficiency, he says. Businesses may be buying more CPU than memory because memory costs more up front, but that may be short sighted if extra memory and better planning can achieve higher consolidation ratios and ROI, he says.

VKernel's conclusions have to be taken with at least a small grain of salt, because the vendor sells products that improve utilization of virtual server deployments. But Semple points to data showing that high-density deployments can over-allocate memory without running into performance problems.

Overall, VKernel says the three-year cost is $1,500 per virtual machine for average customers, and only $1,000 per virtual machine for high-density customers.


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