This article can also be found in the Premium Editorial Download "Storage magazine: Using two midrange backup apps at once."
Download it now to read this article plus other related content.
Except that backing up one server is different than backing up five, 10 or 15 virtual machines (VMs). The problem is resource contention. "Backup imposes overhead on the [physical] server," says David Dale, chair of the SNIA Canada IP Storage Forum, a member of the SNIA board of directors and a NetApp executive.
Regardless of how many virtual servers are backed up, they're guests of a single physical server and must share the CPU and network resources. One possible solution, suggests Dale, is to "delegate the backup overhead to the array."
VMware's solution is different: VMware Consolidated Backup (VCB). "VCB is a Windows-based proxy host," says Scott Miller, president at Server Centric Consulting in St. Louis. Instead of installing individual backup agents on each VM, you do the backup on VCB, which offloads the backup process overhead to the physical proxy host, which is a dedicated server.
Some observers think the resource contention issue is a red herring. "In theory, it's possible that you could overload the physical machine by doing multiple backups, but we haven't hit that particular pain [point] in the real world,"
| notes Ashley D'Costa, enterprise solutions architect at Mainland Information Systems, Calgary, Alberta, a Canadian systems integration and consulting firm. The virtualization backup problems he encounters have more to do with performance and data consistency.
W.R. Berkley Corp., based in Greenwich, CT, backs up almost 100 VMs running as LPARs on its IBM Corp. pSeries servers with Symantec's Veritas NetBackup agent installed on each VM. "We haven't hit any resource contention yet. I guess we could, but the boxes have a ton of ports," says Tom Whelans, VP of operations at the property and casualty insurer. The backup software is licensed by physical server so it doesn't incur additional licensing charges.
This was first published in September 2008