The 7210 SAS platforms use an index file to store the map that indicates the QoS resource allocation to SAPs. This file is used on reboot to ensure that all the SAPs that were created successfully before a reboot can be recreated after a reboot. Without an index file the system cannot ensure this (that is, without an index file it is possible that all the SAPs that were configured successfully may fail on a reboot after saving the configuration file). The file is stored in the flash memory.
On reboot, if the file is found, the system allocates resources in accordance with the stored map. If the file is not found, the system implements a best-fit algorithm and tries to allocate resources for all the SAPs on a first-come-first-served basis. If the file is not present, it is possible that the saved configuration will not execute successfully after the reboot, because the resources might not be allocated to all SAPs.
The index file used for the QoS map is different from the one used for storing interface indexes.