Sync Up Virtual Servers and Storage


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Rounding up virtual machine images
VM portability and migration also cause server sprawl. It's difficult for a storage admin to know how many VMs exist and where they're located. Because VMs are so easy to deploy, they'll spring up in the unlikeliest of places. VMs may be deployed for testing new apps, for migrating data and applications during maintenance operations, or simply to mirror data to server failover activities. They'll sprawl across the enterprise network, making it difficult to standardize their provisioning, and to maintain and patch them.

"The number of virtual machines we have at any one time varies based on development and other issues," says Iannace. "We might have times when we approach 90 virtual machines, but we are constantly building them and destroying them for either development or test. But the core 75 are what we have in production."

Another feature of VMware Infrastructure 3.5 is the Update Manager, which automates the patching of ESX Server hosts and VMs nondisruptively. Update Manager makes snapshots of VMs prior to patching; if patching isn't successful, it then rolls back to the pre-patching snapshot. The software works with Linux and Windows VMs.

"Right now, patching is a bit of a pain for ESX Server host," says Edson at VariQ. "You have to patch by individual patch release and it's fairly time-consuming. Let's say you want to patch a single

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physical server and reboot it; [VMware] Update Manager will in effect VMotion the virtual machines off the server, patch it and then VMotion your server image back on."

VMware is also getting into the game of managing and abating VM sprawl with the acquisition of Dunes Technologies last fall. Dunes' Virtual Service-Orchestrator 3.1 (VS-O 3.1) is server-based software that allows IT to track the creation of virtual machines and automate processes for managing the VMs.

Bus contention and performance issues
Bus contention and CPU utilization are paramount concerns in VM environments. Because all VMs in a physical server share the same PCI bus and CPUs, performance bottlenecks can crop up as VMs contend for the shared resources.

To lessen the effects of shared CPU and bus contention, it's best to implement hefty dual- or quad-core servers that are PCI Express-enabled. Adding dual- or quad-ported HBAs and Gigabit Ethernet adapters to the host servers can also help--each VM can then have its own IO channel to shared storage.

Brattle Group's Iannace deployed Dell Inc. Power-Edge servers with dual quad-core CPUs. "We've seen some high utilization of our backup servers and have upgraded them over time," says Iannace. "In fact, our main physical server is a dual-die, quad-core system--for eight cores total--because we noticed a lot of CPU utilization."

This was first published in February 2008

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