WHITE PAPER. Header Title. Side Bar Copy. Header Title. What To Consider When WHITEPAPER. Choosing Virtual Machine Protection.

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Header Title

Header Title Side Bar Copy

What To Consider When

Choosing Virtual Machine

Protection.

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Introduction

When it comes to providing data protection for virtual machines, IT administrators are faced with a number of important considerations. They must choose between scheduled, periodic backup solutions or real time replication and high availability solutions; between various levels of availability or recovery; between agent-based solutions or agentless protection; and even between host-level and storage-level replication. These choices are not all mutually exclusive. It is important to consider virtual protection solutions carefully and select the solution that will provide the right kind of coverage for all of your virtual machine workloads.

Real-time vs. Periodic Protection

Choosing between real time and periodic data protection seems to be a simple decision at a high-level, but it really isn’t. Part of the decision is based on your desired Recovery Point Objective (RPO). RPO is a way of defining how much data loss can be tolerated in the event of a disaster. Some business critical servers such as email or commerce servers may require the best possible, shortest RPO (zero or near-zero data loss) but other servers will likely have less stringent RPO requirements. Real-time replication is the best solution to prevent data loss. So, if your data is valuable and you want a very short RPO, real time replication is the solution for you. However if your RPO requirements are longer, then periodic backup or periodic replication is an option. Periodic replication leaves windows of data loss that range from as little as five minutes to one day or even one week (or more).

Some disk-to-disk solutions offer configurable backup/replication intervals of every 15-60 minutes at the low end. These solutions tend to employ snapshot technologies.

It is important to remember that frequent snapshots will have a performance impact.

Thus, aggressive snapshot schedules such as every 15 minutes may not work well.

Another thing to consider when deciding between real time and periodic replication is performance. In some ways, real time versus periodic replication is like comparing a fire hose and a bucket brigade. Ultimately, they can both send the same amount of data and accomplish the same goal over a period of time, but real time replication is more like a hose in that it sends data in a constant stream as needed. Periodic replication is like the bucket brigade that sends data one bucket at a time. Performance is affected in the same way, with either a constant, lower performance impact or a periodic higher performance impact. Traditionally, these periodic backup or replication activities were done only during specific windows of time after hours, which limited the impact on performance. Today, in the 24/7 business world, these windows rarely exist, so it is important to determine whether the server can handle periodic bursts of backup activity or whether the server performs better with a steady stream of real time replication activity.

Availability vs. Recovery

In addition to considering the Recovery Point Objective for virtual machines, you must also consider the Recovery Time Objective (RTO). RTO is a way of defining how much downtime you can tolerate for a virtual machine, or how long you are willing to wait to recover it. Like RPO, RTO will vary depending on the type of application or data on the Real time replication

is the best solution to prevent data loss.

So, if your data is valuable and you want a very short RPO, real time repli- cation is the solution for you.

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virtual machine. Some business-critical virtual machines will require a near-zero RTO while other virtual machines might only require an RTO of hours or even days. Regardless of the requirement, achieving a better RPO and RTO is always desirable for every protected virtual machine.

Availability generally refers to solutions that bring servers back online immediately or within a matter of seconds or minutes. Availability may be performed locally or remotely across sites, and there are solutions for local availability, remote availability, or both.

Recovery is generally related to recovering a virtual machine from a backup image, a task that often requires hours to perform depending on the size of the virtual machine being recovered.

Availability solutions vary and include clustering of hypervisor host servers for local availability, combined replication and failover technologies for local or remote availability, or backup solutions that pre-seed standby virtual machines from backup images. Some of these solutions include health monitoring of the virtual machines, the guest OS, or even individual applications running within the virtual machine. Automatic monitoring allows for failover to occur more rapidly either manually when an administrator is alerted or automatically without administrator oversight. Without monitoring, RTO is dependent on outside means to identify failed machines and bring the related standby machines online, a condition that has an impact on RTO.

Recovery solutions vary in RTO depending on recovery technologies, although these will always provide a poorer RTO than availability solutions. Recovery solutions generally provide additional recovery options such as granular recovery of files, folders, or application objects. Another common feature of recovery solutions and some availability solutions is point-in-time recovery. These allow virtual machines (or data) to be recovered from earlier points in time if necessary.

Agent-Based vs. Agentless Solutions

Agent-based solutions install an agent directly onto each virtual machine in the guest OS. Here, the agent performs some or all of the replication or backup functions. Agentless solutions do not require an agent to be installed on the virtual machine, but instead use virtual hypervisor host-level agents or virtual appliances to replicate or back up other virtual machines on that host.

Deciding on agent-based or agentless protection for virtual machines involves considering several factors. One of these factors is simply whether or not you are willing to install and maintain an agent on every virtual machine in need of protection. Agentless protection is generally independent of the guest OS and therefore protects Windows^®, Linux^®, UNIX^®, or any other guest OS equally. With agent-based protection, there must be an agent available for the each type of OS on each virtual machine in need of protection. If all of your virtual machines are running Windows as the guest OS, or even Linux, agent-based solutions will likely be readily available. If you have a wider variety of guest operating systems on your virtual machines, agents may or may not be available, and an agentless solution may be a better choice. It should also be noted that while agentless solutions require same-to-same platform replication, agent-based solutions allow for cross-hypervisor and cross-cloud replication.

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Another factor to consider between agent-based and agentless protection is granularity.

Agentless protection is generally limited to protecting entire virtual machines or at least entire virtual disks. This includes system page files and other temporary files that do not need to be protected. Protecting this extraneous data requires more disk space, more bandwidth, and more processing. Agent-based solutions are embedded in the guest OS and can offer more granular selection of data therefore excluding extraneous data from protection, and this makes the process more efficient.

Both real time replication and periodic protection can be found in both agent-based and agentless solutions, but agent-based replication and agentless replication options are quite different. Only agent-based replication allows for granular, real time, byte-level replication, which is the most efficient form of replication. Given the inherent efficiencies with agent-based, real-time replication, a very good RPO is easily achieved.

Storage-based Replication Considerations

Agentless replication can either occur at the virtual host level or at the storage level.

Host-level replication allows for granularity when replicating individual virtual disks, while storage-based replication is only granular to the storage volume level on the host. Storage-based replication is block-level and varies between real-time and periodic, depending on the distance replicated and the storage vendor. Storage-based replication often requires matching storage vendor technology at both sites, which may increase the cost of the solution, while agent-based replication is generally storage agnostic. On some virtual hypervisors such as Microsoft Hyper-V, agentless real-time replication can be performed directly between hosts, although on other virtual hypervisors such as VMware vSphere ESX, agentless replication is generally limited to the snapshot-based periodic variant.

VM Performance Considerations

One argument that often seems to enter the agent-based vs. agentless discussion is performance. Some agentless solutions would have you believe that there is no performance impact to virtual machines because the protection is handled from outside the virtual machine. While it is true the replication processing is not done within the virtual machine, there are backup and replication processing operations including snapshot operations on the virtual host server that do impact the virtual machines on that host, either directly or indirectly by using server resources and performing operations against the virtual machines themselves. Some “agentless” solutions actually do use agents within virtual machines, at least on a periodic and temporary basis, for dealing directly with in-guest applications and data. The performance impact of agentless solutions is not really eliminated; it is simply rendered more indirect. Agent-based solutions have a direct impact on each virtual machine running the agent. Because agents can be more granular and offer byte-level, real time replication as an option, the performance impact can be mitigated versus less granular agentless solutions that impact the whole host.

Ask Yourself These Questions:

• How critical are my virtual machine applications? How much downtime can I afford for each virtual machine?

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• Do I have one set of requirements or SLAs for my virtual machines and data or do I have multiple SLAs?

• Would my current network bandwidth support periodic backup/replication spikes or would it better support real time replication flow?

• Is storage-based replication a good fit for my virtual machines or would I prefer the protection granularity of host-based agentless or agent-based replication?

• Should I use agent-based replication for better replication efficiency or host-based agentless replication for simplicity?

• Will the solution serve as a single agent-based or agentless approach, or does it provide multiple approaches for different virtual machines?

Summary

Not all virtual machines are equal. Like physical servers, some have more stringent requirements for RPO and RTO because their application services and data are more business-critical than other virtual machines. Replication technology can help ensure the availability of your virtual machines and protect the integrity of your data. Different types of replication engines present their own advantages and disadvantages. You must carefully weigh the benefits of real-time over periodic replication, and understand the differences between availability and recovery. You should also have a good understanding of the differences between agent-based and agentless solutions, and host versus storage-based replication. The likelihood of selecting a replication solution that best fits your needs is greater if you ask the right questions.

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About Vision Solutions

With over 25,000 customers globally, Vision Solutions is one of the industry’s largest providers of business continuity and information availability solutions for Windows^®, Linux^®, IBM^® i, AIX^®, and Cloud environments. Vision’s trusted Double-Take^®, MIMIX^®, iTERA^® and brands keep business-critical information continuously protected and available. With an emphasis on affordability and ease-of-use, Vision products and services help customers achieve their IT protection and recovery goals, which in-turn improves profitability, productivity, regulation compliance and customer satisfaction.

Vision Solutions also offers the tools and competency needed to migrate complex, multi-layered computing environments. These solutions are designed to eliminate the strain on resources, dramatically reduce server downtime, and offset the risks associated with migrations. Regardless of OS or hypervisor, Vision Solutions offers the technology needed to make every migration a success.

Vision Solutions oversees a global partner network that includes IBM, HP, Microsoft, VMware, Dell and hundreds of resellers and system integrators. Privately held by Thoma Bravo, Inc., Vision Solutions is headquartered in Irvine, California with development, support and sales offices worldwide.

For more information call:

1.800.957.4511 (toll-free U.S. and Canada) 1.801.303.5108 or visit visionsolutions.com Also find us on:

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