An increasing number of business or mission critical servers are being virtualized. As a result, maintaining the right level of uptime for these systems is a key requirement for virtualization administrators to address. In this brave new virtualized world, time tested techniques like establishing recovery point and recovery time objectives are as critical as ever.
What are RPO and RTO?
RPO is the desired point in time that a failed server needs to be recovered back to. The longer the RPO the more data or transactions are lost when restoring from the last backup. RTO is the set amount of time to restore the application to a working state so that users can return to work.
For example, if a server fails at 4:00pm on Tuesday, and the last backup was at 11:00pm on Monday, the earliest possible recovery point is 11:00pm Monday. All the data that was created or modified from 11:00pm until 4:00pm will have to be recreated. For some virtual servers this amount of lost information may not be as bad as it may sound. If there were a limited number of changes made, and if there was a paper trail from which that information could be rescued, then bringing the impacted application back to a current state may be feasible.
For other applications, it can be a catastrophic situation. This can be especially true if there is a lot of data to be re-entered or if there is no audit trail, like paper, that would allow this information to be recreated.
RTO is the actual time it takes to move this application back to a state that it can be accessed by its users. This essentially involves the transfer time from the backup or secondary storage target, across a network, back to the primary storage system. Obviously, the size of the data sets to be transferred and the speed of the network directly impact how fast that data can be moved.
RPO also impacts RTO since, depending on the frequency of data capture, there will likely be some sort of re-keying of information to bring the application back into a production state. Also, the data capture quality impacts RTO. If the data was not in a backup state, then some sort of indexing may be required. That indexing typically needs to complete prior to the application being brought back online.
Understanding RPO and RTO are essential to creating recovery objectives for your virtual environment. Not all applications are created equal. Storage Switzerland has prepared a detailed guide to establishing these recovery objects. Please fill out the form below and we will send you an exclusive copy of the guide.
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