Agents. Agentless. VADP integration. VSS integration. Image based backups. File based backups. Hypervisor based snapshots. Array based snapshots. Host based backups. Guest based backups. It’s no wonder why backup professionals are confused about what the best approach is for backing up their virtual machines. With a myriad of vendors, all positioning their own way as the “best” way, it leaves in its wake ambiguity and a good dose of confusion about what an agent is, or does.
With the help of my technical experts here at Symantec, this blog distils the confusion with unbiased information so you can make the right choice for your environment. By looking at each method and highlighting the pros and cons of each, you can make informed decisions without the distraction of smoke and mirrors.
Caution: But before we dive in, it’s important to mention that the phrases agentless backup and agent-based backup can mean different things to different vendors. To truly determine what the best approach for your organization is, you need to look under the cover and weigh in the pros and cons of each method. Don’t worry; we have done the hard work for you at Symantec. Now let us jump in and take a look at each one in turn.
1) Traditional Agent-Based Backup (also known as guest based backup)
Traditional agent-based backup is also known as guest based backup. An agent is installed in every virtual machine and treats each virtual machine as if it was a physical server. The agent in this scenario is reading data from disk and streaming the data to the backup server. This method must not be confused with agent-assisted backups that we will cover later.
There are many people today using this approach to protect their virtual machines. According to ESG1, 46% of all environments are utilizing guest based protection methods with a backup agent running inside the guest OS. Although there are newer methods available, you may be asking yourself why so many people are still using this method.
Verdict: A cumbersome, traditional backup and recovery method, but offers flexible recovery features.
2) Agentless backup (also known as host-based backup)
Agentless backup, also known as host-based backup, refers to solutions that do not require an agent to be installed on each VM by the administrator. However, it’s important to note that the software may be injecting an agent onto the guest machines without your knowledge.
These solutions integrate with VMware APIs for Data Protection (VADP) or Microsoft VSS, which creates fast, high performance snapshots of the virtual disks attached to VMs. The backup software communicates with VADP or VSS and tells it what it wants to backup. VADP and VSS carry out a number of steps and in turn prepare the data to be backed up. The VSS / VADP provider snaps the volume and gives the backup solution access to this snapshot by feeding the file to the backup server. The backup solution then backs up the snapshot.
While it provides recovery for full VMs, files and folders, the recovery of applications and application data can be complex and time consuming. This is because it requires additional processing that engages resources external to the virtual machines. Applications on these hypervisors won’t truncate their transactions logs or perform other database maintenance tasks. An Exchange Server is a perfect example. Without an agent or agent-like executable in the VM gathering metadata about the Exchange information store there is a need for additional processing external to the exchange VM in order to map mailbox data. If you ignore this process, it can result in unmanaged transactional applications that must be manually managed by the application owner, and data that might only be recovered by first restoring the entire VM and its virtual disks. Therefore, one of the key differences between Agentless and Agent-Assisted backups is how the transactional post-processing happens.
Verdict: Good method for protecting file and print servers, but not an optimal solution for VMs with applications. Recovery is operationally painful for applications and application data.
3) Agent-Assisted Backup: Next generation backup (also known as host based backup)
Agent assisted backups are also known as host based backup and integrate with VMware’s VADP and Microsoft VSS to provide fast and efficient online and offline backups of ESX, vSphere and Hyper-V. The primary difference between agentless and this design is its perspective: it pairs the VMware VADP or Microsoft VSS with an agent that gathers application metadata to enable multiple avenues of recovery (full VM, applications, databases, files, folders and granular objects). The agent-like executable in this instance is not carrying out the backup and thus does not impact the performance of the VM. It’s simply handling metadata and necessary post backup processing like log truncation.
The most resource efficient backups are the backup operations done at the hypervisor level and provide some of the following advantages:
Verdict: Excellent method for VMs with applications like AD, Exchange, SQL and SharePoint.
Before I close out this blog, it is very important to understand that backup vendors who utilize VMware VADP or Microsoft VSS to perform backups are not the same. Some are better than others. How good the backup software is will depend on the validation phase. So don’t be fooled in thinking that all solutions with VMware VADP or Microsoft VSS integration offer the same functionality and benefits. A quality backup application that integrates with VMware VADP or Microsoft VSS to perform backups should at the very minimum:
As you embrace virtualization or increase your virtual footprint, selecting a backup solution that integrates with VMware VADP and Microsoft VSS will provide fast snapshot-based image backups of online and offline guest virtual machines. For superior recovery capabilities a solution that gathers metadata and executes post processing tasks is a must. So we’ve learnt that the question isn’t whether you have an agent or other differently named binary in the guest. The question is what is the agent’s function. Jason Buffington, a Senior Analyst at ESG, wrote a great blog on “good agents” and “bad agents”. If you would like to learn more, you can check out his blog here: http://www.esg-global.com/briefs/agent-best-practices-for-host-based-backups/.
In summary, an agent-assisted solution that integrates with VMware VADP and Microsoft VSS is the clear winner in today’s environments where physical and virtual machines require a holistic approach.
Finally, I couldn’t close out this blog without mentioning Backup Exec. Yes – I am biased on this one, but Backup Exec provides a perfect solution for virtual environments with technology that was designed for VMware and Hyper-V. Not only does Backup Exec provide superior data protection for virtual environments, it also provides market leading technology for physical environments too. With Backup Exec you get it all in a single solution. So here’s my pitch. Backup Exec 2012 dramatically reduces the time to recover from small or major disasters by protecting all of your virtual machines and/or physical servers through a single pass backup, while still allowing for individual file, folder and granular object level recovery. In short, it’s powerful, efficient, reliable and fast.
If you have any questions or would like to know more, email me at: email@example.com.
1 Source: ESG Research Report, 2012 Trends in Data Protection Modernization, August 2012.
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