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Blog Post

Backing Up Virtual Machines

What You Need to Know

Virtualization technology is continuing to be adopted for consolidating data center infrastructure and providing a more flexible platform for moving, provisioning and backing up workloads. This has put an emphasis on backup and recovery; because a single virtual host can contain several virtual machines and is even more important to not only protect the individual virtual machines but the entire virtual host. Virtualization has the same single point of failure as some cluster technologies and services: shared disk. What happens to your virtual infrastructure if you lose connectivity to your primary storage unit? The entire virtual host becomes unavailable and that can put upwards of 8-10 production workloads at risk, but it doesn’t have to be that way.

Before the adoption of virtualization, backups could be configured to backup pieces of an application, data or the operating system of a server and sometimes the entire server that included all of the above. The industry now refers to these as virtual workloads as they contain the operating system, application and usually the associated data as well. When the physical server is converted through the P2V process a virtual disk image (VMDK or VHD) is created which is used to spin up that workload as a virtual machine. So, for each virtual machine there is a corresponding virtual disk image that needs to be protected. However, backing up virtual machines is only one part of the process and the other and just as important is the recovery portion. Virtualization has actually simplified the backup and recovery process as you only need to backup virtual disk image to be able to restore as a whole versus trying to backup and recover bits and pieces of a server. Another advantage is that IT managers can usually restore that disk image to different hardware if necessary or an entirely different virtual host server.

This is where workload portability solutions have developed to easily move virtual workloads between virtual hosts for high availability. Products like VMware® vMotion, Microsoft® Live Migration provide the ability to transfer workloads in real-time between similar virtual platforms and other products like Double-Take® Move provide the ability to move virtual workloads between any virtual platforms. VMware vMotion utilizes the replication functionality of the attached storage to replicate the virtual disk images between devices while Microsoft Live Migration is built upon failover clustering technology that allows shared storage between the virtual hosts. The Double-Take Move product is more hardware and virtual vendor neutral as it allows virtual workloads to be moved in real time across any hardware or virtual platform. All of these solutions are effective backup solutions that can easily transfer the entire virtual disk image to another server and spin up quickly to minimize any interruption to production operations.

But the underlying technology to back those virtual workloads up hasn’t changed much. The processes used to backup virtual machines can be used the same as they were for physical servers and are basically broken down into hardware based replication and host based replication. Tape backup solutions aren’t addressed in this article as they have become more of an archive option and don’t meet RTO or RPO requirements necessary for virtual infrastructure. However, once the virtual disk images have been replicated to a designated backup are, tape is often used to archive those disk images to meet certain industry regulatory compliance.

  • Hardware-Based Replication – Some virtual solutions utilize the inherent replication of the direct attached storage or SAN to replicate the virtual disk images offsite to another storage device for backup. This usually uses either synchronous replication or a snapshot type technology that periodically sends scheduled updates to the virtual disk image at the target destination. Synchronous replication sends blocks of changed data and waits for a confirmation from the receiving device before sending the next block for replication. This happens pretty quickly but it usually has distance limitations and requires more bandwidth (because it sends data in blocks verses bytes). This differs from the snapshot process that is usually scheduled to send changes to the virtual disk image on a defined size or time period and only available between like devices.
  • Host-Based Replication – is an asynchronous technology that sits on the virtual host machine and replicates changes to the virtual disks as they occur and then apply on the target servers in the order of the operation they are received. Asynchronous replication is usually transmitted at byte level as well as provide additional compression in order consume less bandwidth than block level synchronous replication. Host-based replication is also more flexible because it is hardware agnostic and isn’t tied into a specific hardware or virtualization vendors, and it can be used for both physical and virtual environments.

Three Tips for Protecting Virtual Infrastructure

  • Flexible Infrastructure - If you already have a disaster recovery solution in place make sure that it is flexible enough to be used for physical and virtual server platforms. Also, make sure that you aren’t vendor locked into something that is hardware- specific and can only talk to other devices like itself. Data center managers maintain a variety of hardware and require workload flexibility to maintain solutions for every environment. Find a solution that is hardware agnostic and will fit existing design infrastructure.
  • Offsite Storage - Most companies already have a co-location facility in place or, at the very least, a satellite office that can be used to receive data offsite for disaster recovery. Whether it is a duplicate virtual infrastructure in the same data center, across the street or another country, having an up-to-date virtual workload backup provides the option for recovery when needed.
  • WAN Infrastructure - How the data is transmitted will be important when protecting your virtual infrastructure. Some synchronous hardware solutions are block-based replication and require more bandwidth and can have distance limitations. Some of the virtual products on the market use a snapshot-based technology that sends data in periodic chunks (verses only changes made to specific files) and can also saturate existing bandwidth during the transfer process. WAN accelerators from companies such as Riverbed and Silver Peak can improve bandwidth limitations.

In summary, no matter which virtualization product you select, make sure you think about protecting those servers on top of just converting to a virtual environment. Selecting a flexible data backup and recovery solution will not only help provide high availability but it can also help data center managers better maintain these systems by having the ability to provision, convert and move the systems near or far. This provides more options for deploying virtual environments, managing them on a daily basis and enabling a better backup and recovery strategy.

More Stories By Brace Rennels

Brace Rennels is a passionate and experienced interactive marketing professional who thrives on building high energy marketing teams to drive global web strategies, SEO, social media and online PR web marketing. Recognized as an early adopter of technology and applying new techniques to innovative creative marketing, drive brand awareness, lead generation and revenue. As a Sr. Manager Global of Website Strategies his responsibilities included developing and launching global social media, SEO and web marketing initiatives and strategy. Recognized for applying innovative solutions to address unique problems and manage business relationships to effectively accomplish enterprise objectives. An accomplished writer, blogger and author for several publications on various marketing, social media and technical subjects such as industry trends, cloud computing, virtualization, website marketing, disaster recovery and business continuity. Publications include CIO.com, Enterprise Storage Journal, TechNewsWorld, Sys-Con, eWeek and Peer to Peer Magazine. Follow more of Brace's writing on his blog: http://bracerennels.com