First, the application servers must be told to empty their buffers and pause their data updates at a consistent state.
Then a quick point-in-time copy of the data must be performed.
As soon as this point-in-time copy is captured, the application servers can be released to perform normal IO operations.
Another point-in-time copy generation technique makes use of snapshots.
Snapshots create almost instant copies of the source volume at the virtual level.
The backup can then be performed using the Besides being a backup source, mirrors are a useful tool for high-availability and disaster recovery tool.
However, the original volume is not protected after the mirror split.
When the data is updated in the original volume, algorithms are used to preserve the data in the snapshot copy (Before the snapshot is taken, the servers are quiesced for a short time and a snapshot index is generated.
At this point, both the original volume and the snapshot volume have pointers to the original data blocks, making the copies exactly the same as expected.
This operation is generally fast, and server operations resume immediately.
When a write operation is pending, that operation waits until the original data is copied to a new block.