When backing virtual machines, you must pay a lot of attention to the applications and data you want to back up. This can take place in three ways:
- With agent-based backup software, in which a software-based agent is placed on each server that needs to be backed up
- With software that integrates with VMware Inc. Consolidated Backup, a proxy server-based approach that offloads the backup process from the physical or virtual machine
- With image-level backups that allow the entire virtual machine and its operating system, applications and files to be backed up
Most backup packages, including CA's ARCserve Backup, Hewlett-Packard (HP) Co. Data Protector and Syncsort Inc. Backup Express, accommodate all of these approaches. Storage managers will often use a combination of approaches to back up their environments -- taking image-level backups or snapshots for disaster recovery, using agent-based software for granular recovery of data, or software that integrates with VMware Consolidated Backup. Each of these approaches has its advantages and disadvantages, users and industry observers say.
The most common method for backing up virtual machines is with the use of a software-based agent, in which a backup agent is installed for each instance of the virtualized operating system. While this approach lets you recover individual virtual machines and the data associated with them, if you install an agent in every virtual machine and the virtual machines are meant by design to be optimized, resources that would have been normally available to a p...
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hysical server for backup are no longer there and performance degrades. Additionally, if enough virtual machines are being backed up at the same time, you can overload the I/O resources of the physical server.
Replacing the agent with a proxy server that offloads the backup process to a separate physical server can help. Many vendors, including CA, HP and Syncsort, have integrated their backup packages with VMware's Consolidated Backup. VMware Consolidated Backup can be used to back up Fibre Channel or IP SAN files without the need to install backup agents on every virtual machine. However, VCB is limited in its capability -- it does not support database applications such as Microsoft's SQL Server or Exchange, and does not support block-level backup.
Image-level backups such as those afforded by CA's ARCserve Backup and Syncsort's Backup Express and CA XOsoft Replication support both file- and block-level backups and databases such as Oracle, SQL Server and Exchange. Because Syncsort's Backup Express, for instance, uses incremental backups and stores only changed blocks, storage requirements and performance overhead are reduced.
William Grainger, network analyst for the Alachua County government in Gainesville, Fla., has used Syncsort's Backup Express for more than five years to back up both file- and block-level data. Grainger is backing up three virtual machines and is planning on backing up more in the future.
"We use the Backup Express Agent to do block-level backups of our data," says Grainger. "We can instantly map a drive to a different server to make data available. With a tape backup, what would take hours takes minutes now. If we have a drive failure, we can use iSCSI to map to the volume on the SAN, take a point-in-time copy and map a drive to it. To the end user, it is seamless -- they don't even know it happens."
HP's Data Protector software supports a wide variety of host computers -- among them are HP-UX, Windows, Solaris, Tru64, OpenVMS, NetWare, Linux, AIX and other operating environments. It supports both VMware Consolidated Backup and agent-based backups. With HP Data Protector, image-level backups of virtual machines are restored automatically to the VMware Consolidated Backup proxy server. To restore this file to its original virtual machine requires a manual copy. HP also offers a freely downloadable Data Protector-VMware Consolidated Backup integration packet that contains scripts and documentation on enabling HP Data Protector and VMware Consolidated Backup.
Syncsort's Backup Express, which supports Unix, Linux, NetWare, Windows and Mac OS X host computers, offers not only integration with VMware's Consolidated Backup, but also a VMware Agent that the company claims is "superior" to VMware Consolidated Backup. Backup Express Advance Recovery capability lets administrators recover virtual machine images from most Windows-based storage systems, including Data Domain Inc., EMC Corp., HP and NetApp. It also provides bare-metal recovery of virtual machines. Syncsort also offers continuous data protection (CDP) and server mirroring using block-level incremental backups.
CA's ARCserve Backup, which supports Linux, NetWare, Unix and Windows-based hosts, offers three virtual machine backup scenarios: backing up the entire ESX Server via snapshot technology; placing agents on each of the guest operating systems; and support for VMware's Consolidated Backup. Like HP Data Protector, the CA VMware Consolidated Backup support requires a manual copy to restore operations to the original virtual machine.
About this author: Deni Connor is principal analyst with Storage Strategies NOW in Austin, TX.
