An IO Filter is a virtual machine component that runs in ESXi and intercepts all IO operations between a VM and its corresponding virtual disk(s). JetStream DR software uses IO Filters to examine currently existing disk data and replicate any new data written to virtual disks.
The use of IO Filters allows JetStream DR software to minimize impact to the on-going IO data stream. It also distributes the work over time, while maintaining the latest profile of the data on protected disks.