This article explains how to determine the appropriate amount of backup storage to allocate for IR.
We recommend allocating 20% of the space used on the VM's original disk if using a VM host as destination or 120% of the space used on the VM's original disk if performing the IR to the appliance directly. You can allocate backup storage for IR at any time as long as sufficient space is available. Once this storage is allocated to instant recovery, it cannot be used for backups. However, if you do not allocate storage until after a VM fails, space might not be immediately available for instant recovery.
Storage allocated to IR can be used to perform any instant recovery job. Once an instant recovery job completes, the recovery object should be torn down, leaving the reserved space available for other instant recovery processes.
To manage Instant Recovery Space allocation please review the following section of the admin guide: