There are a few ways you can use to back up VMware virtual machines. However, there are some pitfalls you should be aware of and these methods can help you to avoid likely virtual machine backup problems
- Schedule your backups: In real life, your servers periodically experience traffic spikes. After three months, you should be able to distinguish patterns of server usage, for example, the traffic may dip significantly during weekends. You should choose backup times when the server isn’t receiving too many requests. This will allow more reliable, faster back up process with very little interruptions. Make sure that the back up schedule doesn’t coincide with high traffic business hours, server maintenance, anti virus scan and others.
- Look for unused snapshots: Snapshots are created by VMware tools, such as VMware Consolidated Backup or vRanger Pro, when the back up process is underway. Data may change inadvertently during the back up process and snapshots can protect us from corrupted data, also from data loss caused by a bad back up. Snapshot changes the status of original disk into read-only, while the data is replicated to a delta disk file. Snapshots are usually deleted automatically when the backup process ends. Web hosting administrators should delete any unneeded snapshot after the back up process is completed or performance issues will ensue. Some 3rd party tools can help administrators to find and delete these snapshots quickly.
- Avoid multiple backups: Some administrators make a mistake by performing multiple VM backups, which often degrades performance significantly. Simultaneous backup can also bring about server crashes due to increased traffic in the vSwitch and NIC. Administrators should always back up one server at a time. If administrators really need to perform simultaneous backups, they need to stagger backups to make sure they don’t use the same RAID groups and file system volumes at the same instance.
- Deal with possible bottlenecks: A good administrator knows spots where bottlenecks are likely in the system, whether invisible or visible. During a backup process, administrators should use resource usage monitoring tools to get an insight on bottlenecks in the system. This will allow them to remove any bottleneck before the next backup session.
- Use SYNC driver properly: Application used to create VMware backups can crash due to improper use of SYNC driver; this may cause the backups to be unusable and corrupted. Skilled administrators should know how to use SYNC driver effectively. SYNC driver in the VMware Tools halts I/O and flushes dirty data, when it creates file system-consistent backups.
- Use quiescing properly: Quiescing is important because it ensures that the disk is in a good enough condition for backups, which can reduce the likelihood of data corruption when the backups are restored. This is essential when transactional-based services, such as Microsoft SQL, are used. Virtual machines can be in a number of possible states during a backup process. To reduce the possibility of data corruption during restore, file system-consistent queiscing flushes dirty memory data and freezes file system I/O, before administrators take a snapshot of the VM. Application-consistent queiscing is more advanced, as it can make sure that everything has been written to the disk a snapshot, this ensures very high data integrity when restores are performed. Some administrators shut down the VM before performing a snapshot, this will make sure the VM is application-consistent.