Improving your disaster recovery posture gets a lot of lip service, but for most companies, not a lot of action. But IT managers are finding that using virtualization software can make it easier – and cheaper – to move disaster recovery out of the planning phase and in to production.
"DR's been on my to-do list for much longer than I care to admit," said John Kutz, director of information services and systems at Minneapolis, Minn.-based Verifications, Inc., a provider of pre-employment background checks. Last year, when the company began to look in to VMware virtualization as a means to improve utilization and reduce infrastructure, Kutz also discovered that virtualization would help them implement DR. That realization sealed the deal. "The ability to do DR drove us to making the [virtualization] selection much more attractive," Kutz said.
Working with VMPowered, A VMware Authorized Consultant (VAC) in Circle Pines, Minn., Verifications began replicating its virtual machines to their disaster recovery site 200 miles away using the SnapMirror feature on the Network Appliance 3020 disk arrays at their primary and secondary sites, which copies the changes made to a snapshot of the virtual machines (VMs).
"What I like is how [virtualization and DR] complement one another – I get my application and my OS in one fell swoop," Kutz said, without having to have an exact replica of server hardware sitting idle at the remote site. "All I know
Array replication vs. host-based replication
But when it came to replicating its VMs, Verifications went down a path that not all IT shops can afford. Array-based replication software typically comes as an add-on license to an already pricey storage area network (SAN) set-up. A replication license on your typical Fibre Channel SAN device usually starts at around $10,000 per device – of which you need two – plus the cost of Fibre Channel-to-IP conversion equipment, said Eric Schott, director of product management at iSCSI SAN vendor EqualLogic. Schott added that EqualLogic does not charge extra for replication on its arrays.
Furthermore, IT managers that choose array-based replication need to pay careful attention to how the replication is configured. At its core, array-based replication doesn't replicate virtual machines per se, but the volumes that they are stored in. As such, virtualization and storage administrators need to ensure that all VM files that need to be replicated are stored in a properly replicated volume.
Host-based replication software is an arguably simpler way to steel virtual machines against disaster.
Gene Barnes, IT manager at S.H. Smith and Company, Inc., an independent wholesale insurance broker in West Hartford, Conn., set up high availability and disaster recovery for six servers using a combination of VMware GSX (now VMware Server) and replication software from Double-Take Software in Southborough, Mass. Barnes installed VMware GSX on a free server and used VMware's old P2V Assistant physical-to-virtual migration tool to create backup virtual versions of the company's Exchange, file and application servers. He then installed Double-Take within the primary application servers and set it up to replicate to their virtualized clones on the GSX host.
Barnes also uses Double-Take to replicate a file server at a remote office in Needham, Mass. back to a virtual machine in West Hartford headquarters, helping Barnes ensure that the file server always gets backed up. "We don't have an IT presence in Needham; by replicating [the file server] down here, we just back it up using our normal SAN and backup software," he said.
Pricing for Double-Take in a virtual environment runs $7,995 for up to five replicated Windows VMs, regardless of where they are running in an ESX cluster. The company also offers a more affordable replication option for VMware users that leverages VMware's own built-in snapshot capabilities. Announced in February, Double-Take for VMware Infrastructure 3 (VI3) runs in the ESX service console and will replicate up to 10 VMs for $2,495.
Other than price, the advantage of running Double-Take from within the service console is that users can replicate any VMware supported operating system – not just Windows -- without having to load any software into the guest, said Dave Demlow, Double-Take CTO. The downside, however, is running within the service console doesn't give the replication software as granular a view of the replicated system.
"When you're running within the VM, there are a lot more things you can do by being aware of the specific operating system, by optimizing failover, and by deciding which files really need to be replicated and which don't," Demlow said. "We can really pick and choose what we replicate."
Ultimately though, keeping the entry cost to disaster recovery low is key, said Chris Ackerberg, vice president of global sales and marketing at Vizioncore Inc. in Buffalo Grove Ill., whose esxReplicator competes against Double-Take.
"We're not going for the top tier of organizations," Ackerberg said – those with the budget and expertise in house to do array-based replication. "We're going for the next group of people that would like their information to be replicated, but don't have a ton of money." In some cases, those can be departmental IT managers within a large organization and "that don't want to contact their SAN administrator."
Vizioncore introduced a new version of esxReplicator last month. Among other features, version 2.0 include better performance, VMotion, DRS and VirtualCenter integration, and the ability to bulk load VM images and resynch if connectivity is lost between the VM and its replica. To keep costs low, esxReplicator copies virtual machine files to an offline VM, Ackerberg said, which is only turned in the event of a disaster. That way, "there's no operating cost, no OS licensing, no maintenance," he explained.
But at $499 per replicated virtual machine, some experienced VMware administrators may still forego a commercial tool like esxReplicator and simply write some scripts that take a snapshot of a VM and copy it off-site. To that, Ackerberg said, "For $500, we give you a GUI and scheduling abilities. Sure, some guy could achieve the same thing using home grown scripts, but they could get disgruntled or get hit by a bus. What we do is take a lot of complicated Linux scripting and wrap it in to a package that any admin can use."
Even with all these choices, what if IT admins are still discontented with their DR options? Stay tuned, said EqualLogic's Schott: at VMworld next September, don't be surprised if VMware reveals new products and functionality that further streamlines the protection of a virtual machine against disaster.
Let us know what you think about the story; email: Alex Barrett, News Director.