Virtualization Technology News and Information
Backing Up the Virtual Machine

Quoting from Computer World:


Backup vendors are ensuring that the latest versions of their software can address both physical and virtual machines, and from an administrator's viewpoint, there is often no difference.

"For the most part, a virtual machine works and acts the same way a physical machine does," says Bob Roudebush, director of solutions engineering at NSI Software in Hoboken, N.J.

But the backup software has to treat the virtual machines differently. For one thing, there is the matter of resource consumption. Running multiple virtual servers on a single physical server results in better resource utilization during normal operations but can saturate those resources during backup.

"The problem is compounded when you have multiple virtual machines competing for resources from the host system during backup cycles," says Tricia Jiang, technical attache for IBM Tivoli storage systems. "Backups from one virtual machine can starve resources from applications running in other virtual machines." To address this, Tivoli Storage Manager can stagger the backups across low-peak windows.

Then there is the matter of what to back up -- each virtual server individually, or the physical server on which they run. Syncsort Inc.'s Backup Express lets users select either mode.

There is also the option of backing up the entire virtual server as a single file. "This method requires fewer backup agents on the virtual machine but is not application-aware," says Kelly Harriman-Polanski, director of product marketing at CommVault Inc. in Oceanport, N.J. "It also requires backup of very large files, which are typically 2GB in size or larger, unless the administrator takes the time to execute an export command to convert the file and zero-out the unused portions of the file."

According to Brian Wistisen, senior product manager in Symantec Corp.'s data management group, the main challenge lies not with the backup itself, but with the process of converting between the virtual and physical environments.

"This is where many solutions face the realities -- and dependencies -- of dealing with all the various low-level hardware devices and drivers necessary to operate the system effectively," he says, "particularly when converting from a virtual state to a physical one."

Most companies are adopting a multi-layered approach to backup. Suffolk University, in addition to using replication, has tape backup for off-line storage and is testing True Image software from Acronis Inc. as a way to achieve real-time imaging. Machettira says traditional tape is the university's third or fourth layer of backup.

"Now that we back up to the SAN, we do it disk-to-disk-to-tape," Machettira explains. "We figure tape is the backup of backups when you send something outside for storage."

Terence Choy, network manager at frozen quiche manufacturer Nancy's Specialty Foods in Newark, Calif., has three VMware virtual servers on a single box running Microsoft's SQL Server. He replicates data instantly between 1TB primary and secondary IP SANs, both from StoneFly Inc. Daily incremental backups are sent to online backup service provider EVault Inc. in Emeryville, Calif. After the initial data upload to EVault, the daily data changes might be as little as 100MB. Choy uses EVault's management console to configure all the backup and restore jobs.

"It operates the same way, whether you are backing up virtual servers or physical servers," he says.

John Buchanon, senior network engineer at components manufacturer Sypris Solutions Inc. in Tampa, Fla., runs 55 servers, including five SAN-connected production VMware ESX servers and 30 production virtual machines running various flavors of Windows and Unix. He runs four to 14 virtual machines on each ESX server.

Buchanon is planning for both disk-to-disk and disk-to-tape backup once he gets additional space in the SAN. But in the meantime, he backs up data nightly to three tape drives using Backup Express from Syncsort Inc. All of the virtual servers communicate with the Syncsort master server by TCP/IP via virtual network interface cards. All of the virtual servers share one or two physical Gigabit Ethernet connections on each ESX server.

"One would expect slower backups, but we haven't seen any significant difference in throughput or backup behavior compared to physical servers of the same class of CPU, RAM and storage," says Buchanon. "Since the master server tests the available throughput per backup task per server, it migrates to the fastest-responding virtual machine at any given time, just as it does with the physical servers."

Read the entire article where they discuss a lot more, here.

Published Monday, March 27, 2006 7:35 AM by David Marshall
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