Public Utility Finds the Power of Virtual Backups

The utility company for Snohomish County District 1, Snohomish PUD No. 1, knows the value of power since it supplies electricity for 300,000 residences and businesses, including Boeing.

But just because the utility produces electricity doesn't mean it gets the power for free, so Snohomish PUD No. 1 found itself in the same situation as many other organizations—wanting to conserve power and reduce data center growth.

Also like many organizations, it decided that virtualization would help address those issues, reducing the number of physical servers employed by having each one host a large number of virtual servers running concurrently and independently of one another.

Since late 2007, Snohomish PUD No. 1 has purchased 28 ProLiant 460 and 480 blade servers from Hewlett-Packard, installed VMware's ESX Server virtualization software, and reduced the number of traditional physical servers and server racks.

Melinda Cooper, senior infrastructure system analyst and domain administrator for Snohomish PUD No. 1, noted that instead of buying 30 new servers over the past year, the utility is now running 30 virtual machines on four ESX Server-based systems.

Cooper's organization is responsible for providing services to internal customers, including the creation of development and testing environments for in-house staff. The servers also run applications such as "cashiering, keycard access, payroll, PeopleSoft [enterprise resource planning], [Microsoft] Exchange and many SQL databases," Cooper told eWEEK.

Clearly, these kinds of mission-critical data and applications need to be backed up frequently, but unless managed carefully, that process can eat up an inordinate amount of time and resources. Cooper has implemented a virtual storage backup system that conserves that time and energy in proportion to the energy and cost savings of virtualizing physical servers.

Technological trade-offs

There are several approaches to backing up VMs, and each of them involves a trade-off in terms of complexity and reliability.

One approach is to install a backup agent as if the VM were a physical machine. Snohomish PUD No. 1 was using IBM's Tivoli Storage Manager and began using the application to back up virtualized servers. However, this presented a number of problems.

Administrators have to use a command-line interface to configure TSM, which is not a trivial exercise, Cooper said. Moreover, TSM makes only file-level backups, while Cooper also wanted full-machine backups.

Another drawback to this approach is that when there are a number of VMs on a single ESX Server host, administrators have to perform the laborious chore of scheduling backups to ensure that the VMs don't compete for resources during the backup period, slowing overall system performance.

Moreover, machines have to be shut down prior to the backup because if the VMs are working when the backup is under way there's a chance that transactions will be missed. Alternatively, administrators can take a snapshot of the machine's VMDK (Virtual Machine Disk Format) file, which represents the whole VM as a single file. In either case, manual scripting of pre- and post-backup processing is required.

While a full-machine snapshot provides for fast restoration of the VMDK files—and thus quick recovery of the entire VM—it doesn't allow individual files or folders to be restored.

This means, "You don't get the configuration files, so if a [virtual] server is damaged, you can't restore that," Cooper told eWEEK. And unless the admin specifically adds backup of the configuration files to the full machine backup of the VMDK files, he or she won't be able to restore the virtual server if it is damaged.