Virtualization And Backup: VMs Need Protection, Too

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Research: 2011 Backup Survey

New Possibilities for Data Protection

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Server virtualization is a clear win for the data center, but it presents a mixed bag of challenges and opportunities for those charged with backing up their companies' data. For example, in our January InformationWeek Analytics 2011 Backup Technologies Survey, 49% of our 420 respondents say they treat virtual servers the same way they treat their physical servers--installing a backup application agent on each and every virtual machine.

Now, that may yield a simple backup architecture, but there's a performance cost when multiple VMs on a virtual server host share network and storage interfaces. When a media server requests backups from several VMs on the same host, all those agents start pulling the requested data concurrently and shooting it out across the network. This will saturate the local and storage area network connections for the virtual server host, not only reducing backup performance but choking other VMs on that host that may be serving users. In addition, this proliferation of agents wastes memory, and when the backup vendor comes out with an updated agent or patch, pity the poor admin.

Hypervisors including Microsoft Hyper-V, VMware ESX, and Citrix Xen have host operating systems or service console partitions that enable 28% of our respondents to install backup application agents on the host. While this method does reduce the number of agents that must be installed and maintained, it still requires that the administrator either shut down the virtual machines to back them up or back up the VMs as open files, creating "crash consistent" backups.

On the hit list of IT euphemisms, "crash consistent" translates to "only as consistent as the data on disk would be if the server crashed." You'll still lose any data cached in memory.

A Better Way?

VMware's first attempt to improve this process, VMware Consolidated Backup (VCB), was a rather clunky piece of software that took a snapshot of the VM and provided access to the snapshot through a Windows proxy server. With vSphere 4, VMware has replaced VCB with a new vStorage backup API that eliminates the need for the Windows server. It can perform image-level or file-by-file backups of VMs by accessing the shared storage that hosts the VMs, taking the load off the virtual server host. The vStorage APIs also allow for block-level incremental backups that are faster and smaller than traditional incremental backups. Just 12% of our survey respondents say they use VMware-specific backup software today, but we expect that number to increase.

Meanwhile, three smaller vendors--Vizioncore, now a division of Quest Software; Veeam; and PHD Virtual--have developed backup applications specifically for VMware environments. Their applications leverage the vStorage APIs and add additional functionality, including individual-item restore for applications like Exchange and SharePoint, replication, and simple restores from a series of block incremental backups. Twelve percent of our respondents use these products.

InformationWeek: Feb. 14, 2011 Issue

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