Traditional models and new tools for virtual server backup

In most IT organizations, virtual servers are backed up in the same way as physical servers in the early stages, but as the number of virtual servers increases, traditional backup methods start to get out of place. In fact, many virtual machines (VMS) reside on a single physical machine and pose many challenges, which do not exist when a separate backup to a physical server exists.





multiple virtual opportunities to compete for resources such as processes, storage, and networks, which are the biggest challenges to data protection for virtual servers. Parallel backup jobs for multiple virtual machines can seriously affect the performance of applications deployed on these virtual machines. When backing up a virtual server in a traditional way, some key features are sacrificed, such as the application of consistent data protection and the recovery of secondary virtual machine level objectives, such as file systems, without having to restore the entire virtual machine. With the proliferation of virtual servers in data centers, IT managers are explicitly called upon to rethink their backup strategies to more effectively protect applications on virtual machines and virtual machines.





Virtual Server Data protection Scheme selection





the current virtual server environment can choose one of the following ways to protect data:





-Virtual machine backup agent





-Continuous data Protection (CDP)





-Backs up the virtual machine images on the hypervisor host through a backup proxy





Virtual machine backup agent. By installing the backup agent on each virtual machine for backup, the way in which the backup is widely applied to the physical server extends to the virtual server realm. Unlike each physical server, there is a backup agent, each of which has its own agent and a backup job that runs independently. This approach is suitable for situations where the number of virtual machines is low, and as the number of virtual machines increases, competition for resources can create performance problems. In addition to being able to leverage existing backup products and methods, the backup agent is the most straightforward way to ensure consistency of application. For many applications, especially non-Windows applications and applications that cannot be integrated with Microsoft Volume Shadow Copy Service (VSS), the backup agent may be the only way to ensure that backup data is applied consistently.





Continuous data protection. CDP products run on each virtual machine are upgraded from backup proxies that run traditional full and incremental backups. CDP products continue to capture changes, compared to traditional backup methods, less load on the host. CDP products can work in file mode or in block mode, and typically provide integration with mainstream applications to ensure timely recovery to a consistent point. In addition to the large backup vendors that have added continuous data protection to their product families, CDP products are provided by smaller vendors, such as Fei Kang Software, inmage systems, Vision FX (acquisition of Double-take Software) and so on.





the virtual machine image on the hypervisor host through a backup proxy server. There are many compelling reasons to back up virtual machine images on hypervisor, unlike backing up virtual machines through backup agents within each virtual machine: it can be effectively backed up under minimal load, eliminating the need to install and manage backup agents on each virtual machine , and multiple virtual machine backups minimize performance problems and resource contention by backing up all virtual machines centrally on the host. In order to split the backup task from the hypervisor host, it is often replicated or mounted to a backup host or proxy server using virtual machine snapshots to reduce performance impact during backup execution.





However, virtual machine image backups on hosts are usually the only acceptable, if the virtual machines can be backed up in a consistent state; all major hypervisor vendors have added silent functionality to snapshot virtual machine images. Another virtual machine image backup challenge is to restore granularity. Some backup products can only restore virtual machines, while others can restore the goals of the secondary virtual machine category, such as files. Consistent application data protection on each virtual machine is more challenging than using virtual machine image backups to compare backup proxies on virtual machines. Applying consistent data protection is often subject to integrated VSS. Non-consistent backup is the only option for applications that do not have integrated VSS, and if application consistency is essential, select the backup agent on the virtual machine.





If this is not the case, virtual machine image backups based on the hypervisor level will become a trend, and the backup task can be stripped to the proxy backup server, and as the number of virtual servers grows, it becomes more important. The different mechanism makes the xenserver of Citrix, Microsoft's Hyper-V and VMware's vsphere virtual machine image Backup's efficiency and function are obviously different.





VMware Vstorage Data Protection API





for VMware, data protection has become a pain point until vsphere 4 is resolved. Prior to this, VMware provided VMware Consolidated Backup (VCB), which was used to offload backups from the system management program to the proxy service, but was not widely adopted because of some major flaws. With VCB, snapshot images of virtual machine disks (VMDK) are generated and replicated in a full copy to the proxy server running the backup. Splitting the backup to the proxy server minimizes the impact of the backup on the virtual machine, but requires additional storage to store snapshots. "VCB is clumsy, and the biggest problem is how to determine the size of the proxy server that all snapshots need to replicate," said Lauren Whitehouse, a senior ESG analyst.





vsphere 4 vstorage APIs for Data homeowner (VADP), a successor to VCB, overcomes VCB's shortcomings. VADP no longer needs to replicate data to the proxy server; instead, snapshots can now be mounted directly to the proxy server, where they are backed up to disk or tape. VCB only supports full snapshots of VMDK, regardless of how it changes, VADP supports a snapshot of efficient change block tracking (CBT) functionality. CBT preserves the traces of change at the block level in the VMDK and makes efficient snapshots of changes only.





vsphere 4 is fully integrated with VSS to provide application-consistent snapshots for applications that are running on virtual machines that have activated VSS. However, to be able to take advantage of VSS, you need to install VMware Tools.vsphere on a virtual machine and communicate with VSS through VMware Tools.





VADP back up a virtual machine, a "quiesce" command is sent to Vsphere, which tells the virtual machine to write the data in memory to disk and no longer accepts write Io. If VMware tools,vmware Tools are installed on the virtual machine, this "silent "is passed to applications that have activated VSS on the virtual machine and" freezes "the application on the virtual machine. The snapshot is then executed, and the "freeze" of the virtual machine and the activated VSS application is lifted when the snapshot completes. Finally, the snapshot is mounted to the backup proxy server, which is then backed up to disk or tape.





VADP is widely supported by Third-party backup applications. In addition to major backup application vendors (Arkeia Software, CAs, CommVault, EMC, IBM, Quest Software, Bakbone, and Symantec), smaller vendors like PhD Virtual Technologies and Veeam software also provide backup applications for virtual servers that support VADP. In addition, VSPHERE provides its own backup tool, called VMware Data Recovery (VDR). VDR is delivered as a virtual tool for performing snapshots and backup-to-disk goals. VMware has positioned VDR as a low-end backup product.

(Responsible editor: The good of the Legacy)