Virtualize disaster recovery


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Disk and tape backups

While tape backups are used less frequently today for disaster recovery, they're still useful for storing data offsite in a secure location. The most effective way to back up a VM is to back up the single large virtual disk file (image level) at the virtualization layer, rather than the traditional method of using an agent inside the guest operating system (file level). Image-level backups are very useful for disaster recovery as they provide a bare-metal restore capability for virtual machines. Instead of having to restore physical servers one by one, you can restore them all to a single virtual host. While using tape for DR is slower than other alternatives, it's still a low-cost way to restore multiple virtual machines. A disk-to-disk recovery is much faster than tape, and is very similar to VM replication as a virtual machine's virtual disk is mounted and then copied to another disk storage device. But, unlike replication, this approach is usually run on a scheduled basis and can be done incrementally or as a full backup. The disk target that's used can then be backed up to tape or copied to a DR site and used to quickly restore virtual machines as needed. Some apps that support this method include:

  • EMC's Avamar Virtual Edition for VMware supports backups of both physical servers and virtual machines by operating at the guest OS or VM layer, and can also globally dedupe backup data.

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  • It can also do physical-to-virtual (P2V) and virtual-to-physical (V2P) recovery for maximum flexibility.
  • PHD Virtual Technologies' esXpress also does both backup and replication, providing data protection and business continuity.
  • Symantec Corp.'s NetBackup has very good virtualization integration and supports both disk-to-disk and disk-to-tape backups. It supports both physical and virtual servers, and can perform both image- and file-level virtual machine backups.
  • Veeam Backup & Replication provides disk-to-disk backup and takes advantage of many of the new features in vSphere.
  • VizionCore vRanger Pro is VizionCore's dedicated disk-to-disk backup product for virtual machines, and it supports many of the same features as their vReplicator app.
  • VMware Data Recovery is included with some vSphere editions. While not as feature-rich as other products, it does provide dedupe as well as good integration with vSphere.

Simple and built-in methods

There are some very low-cost and simple alternatives for virtual DR, as well as some built-in tools in vSphere. At the most basic level, you can use scripts to take a snapshot of a VM's disk to deflect writes to it and then copy the data using FTP/SCP to another disk target such as a CIFS or NFS share. The disk target could be as basic as a removable hard disk that can be transported off-site or a device at a DR site that you copy to over a network connection. Once the virtual disk files are at the DR site, you load them on a virtual host and you'll be up and running. VMware vCenter Converter is another tool that can be used to copy a physical server or a virtual machine to either a disk target or a virtual host; it's not very sophisticated, but it can be scripted and scheduled to make copies of servers. vSphere has some built-in high-availability (HA) and fault-tolerance technology, as well as VMware VMotion. Those features currently all require a local-area network (LAN) and aren't suitable for long-distance wide-area network (WAN) use. VMware has announced its intention to enhance the features to function over slower WAN networks.

This was first published in March 2010

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