One key to solving this problem, Taneja says, is "wide striping" technology, which distributes the I/O load across many disks, rather than just one or a few. Wide striping can help eliminate storage bottlenecks caused by multiple VMs residing on the same physical server, and thus allow higher VM densities.
Taneja says the storage industry was "like a deer in front of headlights" when the data access problems caused by virtualization emerged. But much progress has been made in the past 12 months, he adds. While the likes of 3Par and Compellent were on the cutting edge, established vendors such as EMC and Hitachi Data Systems are now following suit and incorporating at least partial storage virtualization into their existing product lines through firmware upgrades, Taneja says.
At Brandeis University in Massachusetts, which has virtualized nearly all of its workloads with VMware and Xen, director of networks and systems John Turner says he went with a Compellent storage system largely because of its thin provisioning and snapshot technology, which greatly reduces the amount of data needed to store virtual machine disk files.
"Storage is a huge burden on virtualization," Turner says.
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